I’m so sorry to hear you’re feeling this way @Cupcake00. I think most of us have been in this exact place more than once in our lives. It can feel like a catch 22, an overwhelming situation saps us of motivation but we need to bring about a change to motivate us. I also think it’s normal to hark back to a happier time which could be why you’re thinking of your ex.
I’m just coming out of a situation that killed my self-esteem ((now ex)best friend and ex who was also a lifelong friend) and I was pretty devastated for a little while. But, I have a milestone birthday coming up and I am just sick to death of hurting over people who treat me badly. I don’t want to waste any more of my life in pain. I want to live.
So, I joined a diet club and more recently an exercise class where I’ve met loads of really lovely women that could eventually turn into friends. I’ve lost a lot of weight and my confidence is soaring. I’ve taken up drawing again for the first time since school to discover that I’m still pretty good. I’m not happy at work but I'm enjoying myself too much to do anything about it just now.
All this is to say that you can build a life you’re happy with. Not all at once and not straight away but little by little. To me it sounds as if a job change would really help. Perhaps one with better pay and less hours to free you up a little for hobbies and exercise? I know it’s daunting putting yourself out there but just the process of doing something for yourself can switch your mindset and encourage you to keep going.
I'm receiving counselling at the moment and something that my counsellor said that really helped me was to talk to myself as if I’m a friend. So I started telling myself how proud I was of me for surviving so much trauma, for putting myself out there, promised myself that even though I was hurting, I would turn it around and come back even stronger. Plus a bit of self care like painting my nails, having a hair cut etc. can help you to feel better about yourself. In other words, show up for yourself and remind yourself that no matter what, you have your own back.
Sending lots of love and strength your way for brighter days 
P.s. Here’s something I saw on FB recently that really resonated.