Choice: treat arthritis or try to be a mum ... thoughts needed

Hi, all - really hope that most (if not all) of you are having a good day today.

Would really appreciate some thoughts.  Due to fertility issues for me and partner, we've had five lots of IVF since April 2008.  No joy.  View all round is that my RA is the reason it's not working as my body goes crazy - v high temp - when the embryos are implanted.  Since the last IVF, my arthritis has flared up and has now spread to my right hand and left jaw.  (Is already in both knees, hips, elbows and shoulders.) 

As of yesterday, I'm also being tested for auto-immune thryoid disease.  Though easy to treat, it can cause complications in pregnancy.

I am allergic to arthritis meds safe for pregnancy so am relying on local and deep muscle steroid injections.  These, together with the fertility meds, have made my weight rocket.  It's gone up by nearly 2.5kg since the beginning of June so I'm over 83kg.  (My normal weight is around 70kg.)  This concerns me not only for all round health but also a) effect on my joints and b) added problems if I were to get pregnant and had to carry even more.

My rheumatologist wants to get me onto methotrexate asap but this is not safe for the reproductive system.

So I feel like my choices are either a) be selfish and think about what's best for my body (which would mean giving up on dreams of motherhodd) or b) try again to get pregnant, knowing that I could have complications due to weight and thryoid.

Has anyone else been in this situation?  Can anyone help me decide what to do?  (I'd add that, due to my partner's age, we've probably only one last try to get pregnant available to us as he doesn't want to be a Delapidated Dad.)

Feeling terribly low about it all.  I've never complained about having RA as, since I've had it since age 6, have just accepted it as one of those things.  But now feeling like someone's got it in for me and really need some respite.

Don't wish to get anyone down so apologies for miserable post. 

Emma