Hi Jami,
I'm in a similar boat as you, although I haven't had the medical problems you've gone through.
I'm 71 years young. I did the Paleo thing for a few years, then went totally raw, then tried Dr Fuhrman's plan and Chef AJ's, before stumbling onto Dr McDougall. I started the MWL plan near the end of last December at 180 lbs, 5' 2". Truly a little round thing! In the beginning I "gained" weight. When I did lose a pound, I'd gain back two. It was so frustrating and I wanted to give up, but lo and behold, my son and family started eating basically the McDougall plan and their weight dropped like rocks. I assumed then that my problems had something to do with my age, and the fact I'm not as active as I used to be. Not sure that had anything to do with it at all, but thinking like that was enough to make me hang in there devouring all the information I could on Dr McDougall's website, videos and especially this forum. Thus far I've still lost only right at 16 pounds, in 8 months. Very slow, compared to some others, but I honestly don't care anymore that it's going slow. At least it's going! Eating this way has changed my life in so many good ways. I feel so much better, extreme acid reflux has gone, carpal tunnel is history, and I've lost a lot of inches and now shopping for new clothes. I love the food, the ease of preparation, ease of clean-up, the fact that it's so inexpensive compared to what I was eating before. I'm excited about the long term, and I know without a doubt I'm adding a few extra years to my life. That's super good, since I now have a life again. Like you, I'm in it for the long haul.
I hope if there is an underlying cause that you aren't losing, you will be able to discover what it is. I've read here on the forum that thyroid problems can be a factor in one not losing weight.
Whatever happens, I know it's going to pay off for you in the long run.