How do you cope with the thoughts?

I have been on an antipsychotic for over 3 years now. While I have not had many (1 per month, if that) hallucinations, my thoughts are seeming to get more and more out of my control. For example, I won't get dressed while my computer is open because I think the CIA is watching me through my computer. I think my fiance (who is very supportive) has put cameras in our room to watch me while he's not here. I'm afraid to listen to anything through some else's headphones because I think that they can listen to what I was listening to when they put them on again (and I don't listen to anything bad). I constantly think that people don't like me because of the slightest thing. I smiled at my prof the other day after my exam and she didn't smile back so I immediately thought that she must be angry because I finished the exam so fast. This is only the tip of the iceberg.

I'm just wondering what you do to cope with thoughts like this? My fiance is very good at setting me straight, but sometimes he can't. Any advice is greatly appreciated :)