I need advice badly

Me and my ex broke up in April exactly 4 months ago. He made moves on my best friend in a physical way after six months of dating. She also told everyone that he had touched her thigh while me and him were talking and that she was too scared to say anything. The part my best friend left out is that while I was laying on him that day, she was grabbing and holding his hand literally behind my back next to me, and later, actively encouraging me to get w him. She also has had a boyfriend and ever since April I’ve been given an ultimatum by my friends. Basically never talk to him again. If you do, we are not your friends anymore. He has changed and grown a lot since then. I’ve had to do so much healing and I don’t think I’m done. After everything cooled down, and I had some time to think and have the difficult talks with him we decided to stay in contact to support each other through this as it was all over my school and rumors were being spread. I wouldn’t exactly say my friends were there for me at all. In fact the day after we broke up, they all hung out without me. I felt so alone the past few months and I’ve noticed that my friend group has basically isolated themselves. About a year ago I was invited on their family vacation for this July and I decided to go. my best friend always makes it seem very supportive towards me with my decision, but at the same time that ultimatum and her true feelings are always on my mind. Was the ultimatum they gave me the night we broke up out of anger? What he did was wrong and he was battling with lust but out of all people I know the hurt he caused. Is it wrong to try again? Ever since then he has shown nothing but devotion and I can’t tell if I’m just being stupid, and I’m far from naive but I truly believe I genuinely love him. my best friend constantly tells me that she doesn’t care about it anymore. She even contacted him to say that she holds nothing against him. Regardless I’ve always been treated like it was my fault. And that what I choose to do with my life determines whether I can keep friends or be shunned. I know they talk shit about me and it doesn’t bother me so bad but I live in this constant state of anxiety and it hasn’t stopped for so long. I think I would’ve been able to handle the breakup better if it weren’t for how my friends treated me. he was also asked by my mom to come on our family vacation and “surprised me“ she constantly tells me to just try again with him, and that their opinions don’t matter, but after vacation , I have been living with this hole in my chest. I have prayed and begged to God for an answer, but I don’t think there is any easy one and I just need some advice.