Confused

[Mystery1221]

Me and my boyfriend have been together for a little over 2 years and were very commited to eachother. But here is the short version of the story. He and his ex starting talking about a year into our relationship but it was not a big deal, then they went on 2 week school trip and became even closer and were together the whole time. This made me uncomfortable so I asked him to back off a little, recently I found out that he did not tell me he was going with her and 1 or 2 other people to her youthgroup even tho he said he'd back off, I didn't know this then tho. A few weeks later I'd heard rumors that led me into asking him not to speak with her for some reasons. He told me he did stop going to her youthgroup however.

But the problem was a few days ago after school, usually my boyfriend walks me down the hall till we leve but this time he said goodbye n kinda hurried out the door, which I thought was weird but didn't think anything of it, I left a few minutes later n found him and his ex in the parking lot talking In his exes car and planning to go and talk to a mutual friend who was having problems, we had a little fight about this because he promised now to talk to her then he went behind my back about this, if he would have explained it this wouldn't have botherEd me tho. Trust is huge for me so this hurt, he felt really bad tho and cried for days barely sleeping until a few days later when we sorted it out, I ended up talking to her and finding out the rumors were not true so I said he could talk to her again, however he still said he'd back off cause he knew I didn't like it even tho it doesn't seem he Is backing off much. Is it ok that I forgave him for going behind my back? And it still bothers me when they talk but I don't know what to do about it. Help please