Catastrophic Thinking

This is my first post and im not sure what to say. Im driving myself mad with my thoughts. The biggest thing is my Gay bestfriend whom I live with and have for multiple years is so important to me. My old bestfriend left me in an awful way and idk how to not hold on so tight or fear he doesn't want me in his life. That he prefers someone else. That someone would turn him straight and hed leave. None of this makes sense. Why wouldn't he want to go on a vacation with me but with someone else. I am scared they talk about me and I find myself obsessive of "what if they blank". What if he secretly hates me and is trying to find a way to get me out of his life. I think and think and think and think IT never stops.