Lonely in my relationship and finding it hard to decide if I should stay or leave

I have been with my boyfriend for 15 years. The first 4 or so years were perfect. When we met I had a 3 year old son who he built a relationship with and life was good. He moved in.

Then we decided to try for a baby. The pregnancy was fine, although I remember feeling like I wished he would show more interest in buying baby bits and decorating the nursery.

After our son was born I had pretty bad PND. I was really quite unwell and had anxiety and panic attacks. I don't feel like he supported me and he would just say to me during a bad episode that he shouldn't have to put up with me treating him that way. I fully agree, but I desperately needed help.

I managed to get on top of it after more years than it should have taken. Our relationship was stuck in this loop where things are ok and then as soon as something little goes wrong or we have a disagreement I spiral and panic, his response is to shut himself in our room on his phone and shut down. I feel like I've lost trust that he's got my back no matter what. Eventually when I bring up the conversation after days of us blanking each other he will first be defensive and then get upset and apologise and things are ok until the next fall out. I don't feel like we ever resolve any issues, just patch it up and brush it under the carpet.

The other big issue is my now 18 year old son. He has no contact with his Dad so my boyfriend has been the only person close to a father figure. After our son was born I felt he really stopped trying with my eldest and it breaks my heart that he doesn't have the relationship with him that he has with my youngest.

As COVID hit her was already having a hard time with anxiety. I am almost certain he is autistic and gay and he is having a hard time finding himself. After COVID he started refusing to go to school and didn't sit his exams. Since then he has barely left the house and is deeply depressed. He has on a few occasions sent me messages that he doesn't want to be here anymore. I am doing all I can to encourage him to seek help. I find a reason everyday to start a conversation, wake him up and get him out of bed.

The only interaction my boyfriend has with him for years now is to call him down for tea if he's cooked. I have bought it up so many times. He had an alcoholic father and says when he shut himself in his room as a child he was trying to stay away from his dad so he doesn't want to go into his space.

We just bought a house together last year, again this is something I have pushed for and he dragged his heels for a long time.

We used to talk about getting married and were engaged before my son was born. I stopped wearing my ring around COVID when we had a big fall out and i asked him to leave. He moved out for a week and had a breakdown, told me he thought about killing himself so I felt I had no choice to let him move back in when really I was quite relieved that I thought we were separating. Every argument he talks about proposing again and honestly I hope he doesn't as I can't say yes.

I am desperately unhappy and lonely in my relationship. I feel that leaving would be best for me and my eldest but would tear my youngests world apart. I try to be positive but this negative feeling never goes and it's dragging me down.

I realise that is a long message and honestly it just feels good to write it all down!