Ok, the only form of exercise I really enjoy and that I'm good at is swimming.
However, I've got a wrist injury which is made worse by having muscular problems down my left side. And, at present even 45 mins of swimming leaves me in agony.
So, is there anything I can do to try and build up strength, or even push past the pain?
It is really doing my head in :down:

Don't push past the pain. Seriously. If it hurts, it means you are doing MORE damage to your body.

Cross-train and give you wrist a few weeks to heal up. Also, spend some time thinking about how the injury might have happened and how to avoid it.

Well basically, I have on going tendonitis and shorter muscles on one side. I've been told I can treat the symptoms but there's nothing I can do to fix the root of the problem.
I just ..hate the idea of having to have weeks/months at a time in pain and without being able to do the things i like.

Yeah, I went through the same thing. It really sucks but trying to work through the pain with tendonitis is likely to make the problem worse. (Caveat, I'm not a physical therapist. If your physical therapist suggests something, you should go through with it.)

Thanks. I feel better just knowing that a) I'm not alone, and b) someone else knows that I'm not being a wimp!

if you find a qualified yoga therapist, then perhaps s/he can help you out. check out iyengar trained teachers first. yoga can do a lot to help heal tendonitis, as well as work out muscles to promote balance.

good luck! and, only work to discomfort, but not to pain. i'm sure you know the difference. :)