Welcome aboard. I hope you find the support that you are looking for here.
I too have bipolar and when I was first diagnosed it was very hard for those around me to understand that it was very hard for me to control my actions.
What helped me the most was talk therapy. It sounds to me that you could benefit from this as well since you have a lot of insecure feelings and are having a hard time dealing with your mood swings. Of coarse medication adjustments are key but you also have to make an active effort at trying to control your behavior. Medications aren't going to do all of the work. Therapy will help you learn ways of managing your outbursts.
That is what your boyfriend needs to see is that you are catching yourself during these moments and trying alternative things to try to avoid situations like that.
In the end...your boyfriend has the last call if he is willing to work through your illness with you. You've only been with him 5 months and this is a lot for him to absorb and he is seeing you in a whole new light and it's not a very pleasant one. You can try to give him information about your illness and get into therapy and maybe he might have a change of heart but it takes two people to make a relationship work. You have to work out issues for yourself and he needs to figure out if he is willing to walk through this with you. It is a lot for him to absorb as well and your asking him to walk this walk with you. With bipolar it is a life long illness and those around you need to be supportive of you. He may not be ready for that?
Good luck to you. But please remember, most people with bipolar do incorporate the help of a therapist as part of their wellness plan.
You couldn't have written how I feel too, any better than that! Being in a relationship is sooooo hard for me because of some of the things you mentioned (anger, hurt, irritation, feeling rejected when he doesnt want sex). I know those confusing, hurt feelings. I totally and completely commend you for recognizing all of your feelings and also for trying to understand his feelings. It is incredibly hard to control all this when your medicine is not where it needs to be- DO NOT beat your self up for this right now. Be very gentle and understanding with yourself- that will carry through to how you relate to your BF as well. Do that for yourself 1st and the other things going on will be much easier to deal with.
I am going through a very hard time right now myself and sometimes when I read things I think' umm easier said than done'. But you know what i do? I try anyway, and then I try some more. Things aren't going exactly as I would like w/ my relationship- but I keep trying, some days I don't do such a great job and spend a lot of time feeling sorry for myself. I do not know what is going to happen with my relationship, I do what I can and hope for the best.