For the weight gain, only thing that worked for me was change of diet. I gradually built up swimming, to 50 lengths 2 x a week (sets of 6 with a short rest and sips of water in between). Helped with MH and strength, but didn’t really help with weight.
Obvs discuss with GP. But in case useful, what worked for me is intermittent fasting and a keto-type diet. Never dieted in life, though never ate meat. Was inspired by Michael Moseley. Eat in 8 hour window: for me 1pm to 9pm, as suits my preferences/lifestyle. Weighed myself once a week on Sunday and wrote down, to hold myself to account and see progress.
Lots of water, plus black coffee (mornings) and green/herb tea (afternoons). Cut out all sugar (incl fruit like bananas) and most carbs. No bread at all. Same (homemade) dinners as kids (at least 3 veg), but without the potatoes or with tiny amount of pasta or cauliflower rice. Lots of salads with stuff that’s cheap and keeps well in fridge. Rocket or spinach, dill and parsley, then chop celery, cucumber, pepper, radish, beetroot, toms, avocado, olives, gerkins, plus salad topper (seeds) and chia seeds. Then add different stuff on top, like smoked mackerel (warmed in microwave), tinned sardines, smoked salmon, field mushrooms or prawns pan fried in garlic/chilli flakes, chopped vege bacon, sliced hard boiled egg, cheese etc. Snacked on natural yogurt, apple and nuts. No alcohol (v hard). Lots of herbs and spices.
Dropped from 11 to 9.5 stone in about 5 months. Had been referred to MSK for awful back pain due to prolapsed discs. But after weight loss (off belly) all back pain gone. Two years later, have kept weight off by largely sticking to above, but with odd carbs (e.g. sourdough toast for brunch, odd potato), limited red wine and chocolate rice cakes.
If sleep is a problem, cut out alcohol in evenings at least.