Am I going Insane???

I dont know how to write this, I cant even believe that this worry had taken me this far... But for the past 2 months or so ever since I completely lost my mind after a pot smoking session, I've had this fear that I might be going insane, or maybe suffering from some type of depression. Well I've always thought too deep into everything since high school, but I think this deep thinking has gone too far, and is taking over my entire happy view of life. That time when i smoked that pot, I saw the world completely different. I saw all my once loved, significant items as just meaningless objects(my guitar, television, cd's...). And of course this thought escalated, and I started seeing myself as this small insignificant animal just somewhere within the vast universe. What is troubling me is that I am not just thinking these things, but I truely feel that there is great meaning in them, and that others just dont see it. Whenever I have these thoughts (which can happen without my control) I get a nervous feeling, and feel that I am losing my mind. I also get a strange guilty feeling in my stomach in which really effects my mood. Well anyway, this is really starting to effect my everyday life, and I often feel like i am not mentally stable. all and all, I am not that happy guy that I once was, Im constantly in fear that I am someday going to lose my sanity! please help