This sounds exactly like me, lol. I mean, down to the letter - a few months ago I wasn't doing anything on my thesis, I wasn't making healthy choices to lose weight for surgery...so I understand! It's easy to get caught up in a cycle where you don't feel able to make any movement forward.
I still struggle with it, but I found something that helps. I force myself to do one small thing. So for example, with my thesis, I actually said to myself "OK, just write one paragraph, don't even research it, just write it off the top of your head." So I did. And then I found, once I got going, I wanted to build on that paragraph. I wanted to edit it, add some sources, etc. And the paragraph soon built into a full page. I had to force myself to start on one paragraph each day, but it always ended up being a bit more, and now that it's built up it's almost finished!
I do that with other stuff too. Like when my bedroom is a disaster and I feel depressed and like I can't finish it or even start. I just think, OK, I'm going to pick up three things. Or I'm going to pick up the garbage around my desk. Or clear off something on a particular piece of furniture. I always end up doing more.
Just remember: when you feel like this, the challenge isn't in actually doing things and solving your problems. It's in making the decision to get started. If you can overcome that, and start with just one tiny step, bigger things often follow. I remind myself of that daily, and it's difficult every day, but it's helped me move forward.
