Amanda, I really respect that, at this point in your life, you're looking to try to improve your situation, rather than just feeling hopeless about it. That kind of attitude will take you far. I'm not a doctor or a trainer, so I don't feel really comfortable giving advice in your situation. That won't stop me, of course, but there's my disclaimer. Have you read Mark's Primal Blueprint Fitness yet? If not, read it and see what modifications you need to do to it, so that it will work for your situation. Since they're simple body weight exercises, I can't see why your doctor would object to you trying to strengthen yourself using them, BUT please show him what you're planning to try before you start. It sounds you might definitely need your doctor's input before you try anything new.
I don't know how much you've read on Primal lifestyle, but if you haven't (and even if you have), do as much reading on Paleo/Primal nutrition and fitness as you can. Robb Wolf is a really good author if you're like me and need things spelled out for you with science. Mark's Primal Blueprint is better if you don't need to know intricate details but just want more of an overview on what and how. Mark says that diet is 80% of the equation, and I've been really helped, mentally, by the change in my diet. I just feel more clear-headed, MORE AWAKE, more able to be active in general with the change in my diet.
One thing about Primal/Paleo nutrition is that it really works to reduce inflammation that many foods in the SAD (Standard American Diet) may cause. For example, grain can be causing your body to be in worse pain, since it's very inflammatory. This article from Nourished Kitchen explains it better than I can.
If you don't want to shell out a lot of money for books on the subject, I'd suggest seeing if your local library has any books on the subject, so you can read before you buy.
Motherhood: When changing from pj pants to yoga pants qualifies as 'getting dressed'.