When I used to fight against the thoughts with no help of real therapy or medication, it only made them worse. I did start medication which helped to calm me down more than anything, and the less I was stressing about it, the less the ocd bothered me. It didn't mean I totally stopped acting on the repetative thoughts, but it made it easier for me to deal with and did decrease them as I was less anxious. But I guess that may not work for everyone.

What it really comes back to is you need therapy and possibly medication to help deal with the thoughts. At first they may not go, but it may help to how you react to them and whether you act on them.