I, like you, have obsessive thoughts that are hard to control. Its actually rather debilitating and ruins my damn life if I let it. So I know how sucky it is.
Personally, smoking alot while I would have my "obsessive bouts" did NOT help me. It definitely changed my mind, but I'm not sure for the better. It just made me think of other things, that most of the time weren't much happier.
The best advice is to try it and see what happens. I do know for me, cannabis can NEVER be a substitute for medicine and therapy. What actually worked the BEST for me is CBT (cognitive behavior therapy). My therapist has really taught me how to control my thoughts. I never thought I would see the day where I am in control of my thoughts. Now I just use pot for fun! So much better if you ask me.
None are more hopelessly enslaved than those who falsely believe they are free.--Goethe