aphroditeskiss1

so this is the first time I've really posted anything of any value. This is going to be a long post and a rather hard one for me to share but I need some thoughts and advice from people who are older and more expeirenced than I am.
First off, I am 18 years old and going to college next month. I had been in a wonderful relationship with an amazing guy for two and a half years. I say had because I no longer am. Granted this is through my own actons, nonetheless, it sucks.
Here's what happened: in January of this year I switched to a different school than the one I had previously bee attending. This is where my boyfriend and I met. For his sake, I will call him Ryan. At this new school I met a guy who will be called Nate. Not too much of a big deal. Ryan and I, though we were commmitted to each other, were allowed to see other people. The reason for this being that we are both very young (he is 18 as well) and need to expeirince more. The two rules we had with this situation were that we were supposed to be honest about our situations with other people and that nothing sexual (re: beyond making out) was to be done.
I became interested in Nate. I didn't tell Ryan because I didn't want to hurt him. Up to this point, neither of us had really taken advantage of the situation. I didn't know really how to handle it. I knew Nate was interested in me as well. He had asked me to go over to his house and watch a movie with him. He had led me to believe that his father would be home. He was not. We started making out and then things got out of hand. We ended up having sex. I regretted it from the second that it happened and actually became physically sick on the way home.
This was a one time thing. Ryan I know suspected something was going on, especially as I started acting "weird" immediatly after. The guilt I felt was almost more than I could handle. I have always been prone to depression, and this sent me spiriling into one of the worst episodes of my life. I didn't know this at the time, but I am bipolar and therefore my antidepressants weren't working. This also explains the impulsive behavior that attracted me to Nate in the first place. I want it to be known right now that I am NOT BLAMING MY ILLNESS FOR MY INDISCRESION. I just now know that it is indeed a contributing factor. Anyways, a mutual friend of Ryan and mine found out about it. He confronted me and I admitted to it. He speficifally told me he would not tell Ryan, although he encouraged me to.
Well, the bastard lied. Several weeks later, without any warning to me, he told Ryan. Needless to say, Ryan was very upset. We had our fights, but he is willing and has (as far as I can tell) forgiven me. While we are not back together, things are as well off as I can hope for.
This is my problem: since this original betrayl by the friend (Brian), I have found out about several others. Over the years, he has repeated several things that I confided in him on the strictes confidence to either another friend or to his mother. This greatly upset me when I found out. Many of the things were of a very personal nature and I was very upset about this and the fact that he told Ryan. However, I decided that the friendship may be more valuable than that. He has been lately saying things to me like "oh Ryan is off in some room with a girl he just met. Ha ha...just kidding". He knows comments like this greatly affect and upset me to the point of pusing me to the edge. His rational of it is that I haven't been acting "normal" (the bipolar is what he's referring to). I have repeatly asked him in the clearest of terms not to say things like that to me, as it upsets me. He says ok. Then the next day does it again. I have only been on the proper meds for a week. They don't take full effect for up 3 weeks. Brian knows this, and yet still can't figure out why I'm not acting "normal". He has been saying some very rude things to me lately. Very hurtful and very cutting. The last straw came today. He was telling me about a trip to Ryan's cabin that they, with two other guy friends, are taking with Ryan's step sister and 3 of her friends. He proceded to tell me "He could fuck another girl and you wouldn't even know. Oh wait, he's not you. Nevermind. Forget I said anything." When i asked him why he said that he said (this is a direct quote) "I felt like being an ass." IS THIS EXCUSABLE?? I was unable to stop crying for more than an hour after he said this. I want to cut him out of my life compleatly. Am I being unreasonable and impulsive? Or does he deserve this? A quick responce would be highly valued.