First, this is not in your head. It is an unfortunate side effect of pain that many people get sort of encouraged/pressured to think it's all in their head and that sometimes, the medical professionals involved in the care of the people who do that pressure. However, you have received a diagnosis and you are getting treatment, so it sounds as if your doctor is a good one. The fact that your symptoms are getting better with the medication speaks to this being a real case of RA, as well and I know it would almost be a relief to have it be a figment of your imagination, but unfortunately, it sounds as if you're a member of our club now. I can highly recommend a book called The First Year with Rheumatoid Arthritis - it deals with all aspects of living with this disease and can be a fantastic help in getting to the point where you feel in charge of your life again.
Given that you've only been on methotrexate and Enbrel since October may mean that they haven't fully kicked in yet - both can take up to about two months to reach maximum impact. You may want to talk to your doctor about possibly increasing the dose if your pain is due to active disease (i.e. inflammation, redness and swelling of the joints). Your pain could also be due to damage in your joints, which means you'll probably need to supplement your DMARDs (disease modifying antirheumatic drugs like methotrexate and Enbrel) with painkillers. if you have been diagnosed with heart around her, as well, check out the fibromyalgia area of our Chronic Pain site for more information about their condition and tips on living well with it.
You did nothing to deserve this. You did nothing to cause this. You did not bring this on yourself. Getting RA qualifies as an example of the expression "sh*t happens" and the sooner you stop blaming yourself for something that is not within your control, the sooner you can get to the point where you start controlling what you can (check out a post I wrote recently about choices). That includes working with your doctor to get your disease suppressed, taking the painkillers you need so you can get back to living your life, focus on living your life, because being out there being with your family, playing with your kids of the dog, reading good books and laughing every day is what life is. RA is part of what you are, not who you are. Still, it can take a while to adjust to the new reality and I highly recommend counseling to help you find coping skills. Cognitive therapy can be especially helpful for people living with a chronic illness.
Applying for disability is a good idea, especially if your disease is currently so active that you can't work (check out a post I wrote on SSD for links to resources that can help make the process easier). Even if you do get on SSD, there's an allowance for making extra money, so you may still be able to work part-time - make sure you triple check what that amount is, though, so you don't lose your SSD. When you are on SSD, you may also qualify for finance of assistance to go back to school, which may in the long run enable you to get back out there and work if that is important to you. But your first step is to get your disease under control, because without it, everything else becomes incredibly difficult.
Check back here, read our material, the SharePosts written by other users, even write some yourselves - one of the essential elements to living well with this disease is finding people who know what you're going through and we have a very active and supportive community here. We are here to help you and we are here to listen.