Lost In my thoughts

Every now and then I catch myself getting lost in my thoughts.  I know Im not the only one, but at times I feel that I do it more than some. My paranoia will kick in, I start getting lost in the thoughts, and ideas that it brings. I catch myself thinking that this and that are true, but deep down I KNOW that they are NOT true. This has gotten worse within the past couple of years. I know that the thoughts I have are not true, but I often think what if that is, what if that will happen? When this first occured to me a few years ago, I wondered why I feel this way? And when this happens to me I get really depressed and feel low. If this was me years and years ago I would just sit back and pop anti depressants, and escape into a world that I feel comfortable in. And not have to worry about anything or anyone. I used to be my only friend, and depression was my best friend along with pills. But I feel that my paranoia just REALLY gets the best of me, and I think too much into what my paranoia is telling me. And that makes me REALLY REALLY low. And I just feel like it’s going to happen, or that it might happen. But I have someone SO spectacular to talk to and she makes me feel better, because I kow I can talk to her about anything and everything. But I still get this way from time to time. And there are times I try my HARDEST to not let it get the best of me, but it seems to fail. Just thinking about that thought or idea, or whatever it is makes me get so lost in thought. Thats all I will think about for a long period of time, and I will start to think of other things that I know aren’t true, and they get the best of me too. And then I start thinking and getting lost in these new thoughts, not escaping being lost in my first thought. I feel that I’m not myself. I want to not feel this way all the time, and I want to know why I get this way. Sometimes I get feelings or something is bothering me, and I do NOT know why or what it is. The girl I can talk to is truewly wonderful, but I feel Im not telling her how I really feel. I know I can tell her anything, and not be judged, but if I don’t know what’s bothering me and she can tell something is bothering me I NEVER KNOW WHAT TO SAY. I know I can trust with everything I have. Just hearing her voice makes the pain and bad thoughts go away. But sometimes when we talk they seem to come back. And then again I get lost in my thoughts. I try and avoid them at all costs, but they seem to keep coming in and squeezing their way into my mind. But in the end I know that these thoughts are NOT true at all, but sometimes they make me think other wise. But deep down I truely know that they’re not. Why do I get so lost in my thoughts?