I also tend to over-analyze everything (often in a negative way). Don't be too hard on yourself for doing it. I tend to yell in my head: "stop!!!" and just stop listening to my thoughts, if that makes any sense. Often works in a weird kind of way. I just started dating someone and am also super insecure - every time a day goes by in which he hasn't called - it suddenly goes to: "he doesn't really like me," but I try to block out these thoughts. Sometimes we're negative because of critical messages we received in childhood from our parents (my case, definately). Have you talked about this in therapy?