Most Helpful Guy
I can understand how you feel, and at the same time how he feels about the situation. He probably felt he was in catch 22 situation, if he invited you with his ex their you would get jealous, and maybe problems would arise.
I don't think him and his mum were set out in hurting you deliberately, they probably just thought it would be best that you didn't come, because him and his ex go way back and were high school sweethearts, and didn't want his current girlfriend causing any problems, if they were to arise. I am not saying they would think that, but sometimes we don't how certain situation will plan out, even with the best intentions.
I would of probably done the same thing in his position, cause it would of made me extremely uncomfortable you watching me spending time with my ex catching up with things, I would be wondering if you be starting to get jealous of her, and cause fight afterward.
At the end of the day, do you trust him or not. if you don't trust him, then sorry there is no point carrying with the relationship, no matter you love him. trust is the foundation of the relationship, without trust, the relationship is doomed anyway.