I'm so sorry, that's rough luck, particularly the autoimmune thing. With my 3: the first ruined my perfect tits and gave me fat saggy knees, the second gave me sciatica, and the third (surprise) baby hammered my looks at 38.
Advice to op:
I have (and continue) to fight back though! I do a lot of mountain biking, which gives me exercise but also a lot of confidence in myself. I have also started taking my health very seriously; so good diet & supplements, moisturiser (all over), sleep, etc. You don't need to spend a fortune on expensive things, just find a health and fitness routine you like and can stick to. Positive attitude does have a lot to do with it too, which is really difficult if you are stressed or tired, you have to find those things that help to bring that confidence in yourself back; appreciate your abilities and you will have better regard for yourself in general. It has actually worked quite well, ok I don't look like I used to, but I do look like a pretty good 47 year old. My hair is thicker, my nails are stronger, and my skin is much clearer. Also, whether you are fatter or slimmer, everyone looks better with a bit of muscle tone, apart from making your body just work better. Even my sciatica attacks have reduced to just once or twice a year, from once or twice per month from the previous 10 years. Oh, and learn to do kegels, the benefits are many (long lie-ins without having to get up to pee, and better sex- don't underestimate how much better it makes you feel!)
Both my older sisters have done similar, one likes to run, and walks for miles with her dog, and the other rides horses and does climbing, they're 8 and 10 years older than me and both look great.