I think I understand because I sometimes feel the same. I gave up a long term post that would have become a permanent and well paid job when I got caught on with ds 7 years ago. Since then I've had another child, my only friend left to work elsewhere and I've only been able to get work on a short-term basis so even though I work I'm not part of a team and don't get invited out to parties etc. We also have no money so I couldn't afford to even if I was. I am often lonely and feel as though I've lost the person I used to be.
Dh on the other hand works full time and has worked for the same company for almost 10 years. Every now and again he wins trips and attends events as part of his job and at the end of the summer holidays he and a few workmate had a long weekend in a 5* hotel in a hot, sunny resort somewhere in Europe. The green fog of envy didn't half cover my eyes: I had spent the whole of the previous 6 weeks trying to entertain 2 dc (albeit school-aged but still young and need looking after) all day, every day on no money and the weekend if his jolly outing I was treating, and being treated for, headlice as well as having
to cope with one dc having had horrendous d&v and all the literal shit that brings. Add pmt into the mix and I was positively green when dh posted pics of his room and the view from his balcony on fb.
The thing is, if I had had the choice, I would hate to go on a trip somewhere hot & sunny - that kind of holiday is my idea of a nightmare. It is pure jealousy on my part and sometimes I really struggle to cope with it.
I think op that, although a night on the tiles might not be your idea of a great time now, you might still benefit from somehow getting time to socialise and relax and enjoy time by yourself as an adult and away from your baby, even if it's something like a meal or a trip to the cinema or the gym. Try, if you can, not to lose sight of yourself or to only see yourself as your child's mummy; remember that you are still you as well.