mchalel, bear in mind that this is an "uneducated guess" at best, but since some of your problems seem to be similar to the problems I had in my relationship, I thought I'd mention "Generalized Anxiety Disorder". It's a very common disorder that usually hits in your teenage years.
There are many sites dealing with GAD on the web, here is just one I found in a quick search on Google:
http://www.anxietynetwork.com/gahome.html
Basically GAD is "worry about everything". You see what appears to be a problem, and you start thinking about it, building it into something you cannot handle.
In trying to find out what was (is) wrong with myself I stumbled upon info for GAD and it was a real awaking. Medication and cognitive therapy can blunt the effects. Before I would 'cycle' thoughts and build up sceneros, (the worst possible sceneros) in my head until I was stressed beyond belief. Now I'm better able to stop those thoughts and beter rationalize them which is one of the ways I've dealt with my wife's past.
If you need any more info, feel free to PM me.