Struggling with estrangement from 2 adult children and dont know where to go from here.

Hi I have been totally estranged from my 2 grown up sons for over 2 years but the problem has been going on longer than that and I dont exactly know why. It mainly started after my I wish wasnt husband walked out on me after 32 years of marriage and his parting shot was "I may as well tell you but Ive been seeing someone else for a few months. For the first few months they weren't speaking to him but checked in with me, "how are you" " have you slept" "are you eating peoperly" etc. And then after 6 months I met someone new. It was all new and flattering for me after all the time being married. It wasnt dealt with properly on both sides as I wasnt telling the lads where I was or answering messages and calls and I think they resented the fact of me meeting someone. Anyway it all came to a head at the christmas. In my eyes I was pleasing everybody. I didnt want to be in my home as it had been previously, but my boys didnt want me on my own for the first christmas. So we went to my Dads and the lads were there too but I had made arrangements to go and meet my new bloke to spend part of christmas with him too. Well the lads didn't like it and said I was too happy to go off with a bloke I'd hardly met. They were really funny with me and I finally confronted them to ask what was wrong. We had a sit down discussion and aired all our differences and to be fair although things appeared resolved - they weren't by a LONG WAY. So moving on there have been numerous things that have happened and bit by bit they have stopped all contact. My eldest son had another child who was really poorly when he was born but I felt I wasnt included with him and I stepped back as his other grandparents were there all the time and also I didn't feel comfortable there. Anyway he had major surgery after his 1st birthday and they didnt even tell me he'd been admitted, no news of the op or when he came home. That was when he was 1 and I havent seen him since. My son moved house and didnt tell me yet says about me not seeing them. There was also an incident at my youngests wedding but again I didn't even feel that they wanted me there as they came with an ultimatum with the invite. Ive had nothing for christmas, Mothers day or birthdays for all that time and its breaking my heart. I have approached them to try to resolve things but all I get is either awful hurtful messages or just no response. I have now met someone and its been over 3 years now but I mainly live on my own and its awful. I cry most nights because I just want things to be different. Its eating away at me and I just dont know where to turn.