I'm your age OP and recently I was looking dismayed at my body and thinking I looked like my Mum (who was very overweight and had Type II). I have managed to start to turn things around now (had to do similar end of last century, so in theory I know how but I'm post meno now).
Definitely - take it in steps. This is doable but obviously a long term project.
IME the first step is to get enough sleep. I always eat like famine is coming if I don't. It's like, I know it's not what I should do... but I don't care so I do it anyway. If I get proper sleep I look after myself much better.
Then get an exercise routine sorted - a feasible but regular one, e.g. as a start, go for a twenty minutes plus walk every day. Just to establish the routine, then you can swap out a particular day's workout for something else, e.g. weight lifting (which I strongly recommend) or cycling or swimming.
Exercise lifts mood, gets you outside, improves health, gives you time to think and plan, no downside !
Then, thirdly, work on eating sensibly - unprocessed food, protein and veg, three square meals plus healthy snacks.
At this point you'll be feeling a bit better and then is the time to join WW or SW or RC. Set a target of 7-10 lb and then keep it off for three months before trying to lose more weight.
And I know it's an awful cliche, but tarting up stuff that's not waistline related - hair, nails, jewellery, skin blah blah - can cheer you up a little bit and help maintain that long-term motivation.
You feeling crap now is, (in a way) a good thing, as it's providing your psyche with that invaluable things are going to change, starting right now feeling.
Yes, obviously, it would have been more helpful if your psyche had said "eat less and exercise more" several stones ago, but humans don't often work like that. The snackers survived the famines and it's their genes we carry! Eating too little kills you fast, eating too much kills you pretty slowly in comparison, so Nature is biased towards that extra slice being eaten up.
Bit of a wall of text but HTH.