so, advice?

so in this situation i know what i did was childish and wrong, but at the time it seemed like a fantastic idea to try to sleep with his friend (in my defense i told him and he said it was fine -semi open relationship- but then it happend and then he was upset). the problem is now, after everything came out with other friends and due to the one friends new relationship he cant talk to us bc the friend in question had unresolved feelings about the situation. and now while my partner and i are trying to move on and make better and looking to get married this year, people are starting to not want to come and i feel like it's all falling apart bc of the situation and now i just feel like shit- idk what to do anymore tbh our baby is over a year old