Depression is hard to understand unless you've been through it yourself. If you haven't, then realise that you really don't understand what the other person is going through. There's a big difference between 'normal' depression and sadness, when something happens causing you to feel this way, which is a normal response, and clinical depression. In clinical depression there is a change in your brain 'chemistry', for want of a better way of putting it, that doesn't occur with the depression or sadness that most people feel with a traumatic event.
It's important to understand that no one chooses to feel depressed (I'm talking about clinical depression), it is the most awful and frightening feeling, nobody wants to feel this way, and the real point is that your boyfriend, if he suffers from clinical depression, won't be able to choose to be depressed or not. Also, it's not necessarily related to anything happening. For me it's like a light switch, it's either on or off, I more or less know the moment I wake up, and when it's off it seems absurd that I feel the way that I do when I'm depressed. Whatever the reason for depression, understand that this 'switch' causes a real change in the depressed person's brain, they feel awful, behave badly, get irritable, angry, etc. (have a look at all the usual symptoms of depression) and of course, this makes it really difficult for the people around them.
The bad news is that once you've had a couple of clinical depressive episodes (caused in my case, by a long period of stress and a couple of traumatic events) you are likely to have to live with depression for the rest of your life (there are various theories as to why this is, but suffice it to say that there is some kind of permanent change in your brain that causes it, with the emphasis on permanent). The good news, however, is that it's relatively easy to treat. If your boyfriend isn't already seeing a good therapist, then this is an excellent first step. They may recommend various anti-depressant drugs, some work better than others, and it tends to be a very individualized response. Personally, I prefer to be off the drugs, although it can make it harder to manage. They can help, particularly as a short to medium-term solution.
There is a lot of evidence to show that a regular exercise routine can be a very good way of managing depression. I don't know how this works, but it seems to. Other things like getting enough sleep and a good diet helps. Probably the single most important thing is going and seeing a good therapist, and if covered by medical insurance (as it's expensive), making this more or less a permanent fixture. Talk therapy really does help.
What can you do to help? Just being there for him is a big one, and laying off big issues, like whether you're going to spend the rest of your lives together or not. This kind of stuff is not good when the person is depressed, leave these kinds of decisions for when they are well. Stress, in any form, is a big trigger for depression, so don't add to it by trying to force decisions on big issues. And forget about the pep talks, you know, the "you've got to pull yourself out of this" type talks, these really don't help and just tell the other person that you don't have any idea of what they're facing. You don't really have to say anything, just be there for you boyfriend. In time, one realises that depression comes in cycles, like the weather, and like bad weather that blows in from time to time, it passes too. You just have to learn how to cope with it best, so as to make it manageable, and wait for it to pass. There are probably specific triggers, like having a fight, that can start the depression, so look for these patterns and try to identify and avoid the triggers.
Worth noting is that a good therapist can be well worth it, they're much more likely to be able to help than hours of talking to friends, etc. Clinical depression should be treated like a disease, which it is, and you need professional help. If you had diabetes you probably wouldn't try to self-medicate, same goes for depression. Depression isn't a 'harmless' disease either, as suicide becomes a real issue. I get suicidal thoughts every time I get depressed, it's just that I recognise them now as a symptom and don't get to scared of them, neither am I inclined to act them out as I know that they're part of the disease and not really what I feel.
I've accepted that I will have to live with depression for the rest of my life, and that means trying to build the means to cope with it when it blows into town. If you're serious about a future with your boyfriend, you're going to need to do some reading, here are a couple of good links to start with:
http://helpguide.org/mental/depression_signs_types_diagnosis_treatment.htm
what to do to help someone with depression:
http://helpguide.org/mental/living_depressed_person.htm
I can empathise, living with someone with depression isn't easy, but if it's hard for you, it's a lot tougher for them. It isn't something anyone would choose.
Thanks for your messages.
Its basically because his dad cheated on his mum for 6 years with another women and he doesn;t want to be like his dad. It was a wierd scenario and his dad left his mum for this women and then she didnt want to be with him so his parents have been living together as a married couple but not in a relationsip since then and its messed him up a bit.
He has been in constant relationships in his 20s and wants to be single so that he can "feel like a man". This is obviously hard for me to hear and part of me can understand and then part of me thinks if you've found someone you love why ruin that with pointless flings that will probably mess him up even more (he has said I am the person he wants to grow old with but wishes he met me in a couple of years). I obviuosly don;t want to wait around whilst he screws around but i'm not sure it will help him.
He has had councillingng before and for his last relationship. He says he knows what they will say and so won;t do it again. He didn;t love his last girlfriend and was 21 so i can;t imagine they would say the same things.
He text me today, as I got back from our holiday, and said he felt really crap because of all this and do i still want to spend Christmas with him. I don;t know whether to say no and let him have his space and move on :-( Its all so difficult. We're both 26 so pretty young i guess still.