I can't handle my mind anymore

I am currently in a healthy relationship, and all is going well. We are taking it slow and trying to so it right. We are exclusive and dating and all that. We got together in early March, and, from May 1st till September 16th, I was working on a small cruise vessel in Alaska, and we both live in Arkansas. Obviously our relationship was long distance for those 5 months, and now that I am home it would seems as though we are both lost in terms of where we pick up and how to advance our relationship. I see a future with this guy and I do not want to lose him. I have borderline personality disorder with complications from chronic depression, anxiety, and possible psychosis. I am on Prozac and wellbutrin simultaneously to help in treatment for it. Here lately my anxiety has been through the roof and I fear it I'll eventually ruin my relationship because of it.. I can control it for the most part but more often than not it gets out of control and I feel like tearing my brain out of my skill to get it to stop.He said recently that he wants a no pressure relationship and to take it slow, because he made mistakes in the past with moving to fast and he doesnt want to do that with me. He wants to really date and get to truly know each other, and then followed it up with saying he is very busy these days and won't be available nearly as much as we would prefer. Part of my mind understands and accepts this, but the other part will not let me accept it and keeps feeding the paranoia, which is why I am terrified that a time will come that I cant control it and it will come rushing out and ruin my love.Why can't I be happy? Why do I have to have this argument with myself in my head 24/7? I can't hold this in anymore. He knows about my anxiety and other issues, I made that very clear. I don't like being alone. I'm scared of my own mind. I need advice and/or help.