Unfortunately, the goal of reducing the obsessive thinking should not be your main goal. You have no direct control over your thoughts, as you are already experiencing. The more you distress about, try to disprove, or neutralize a thought, the stronger it becomes. The way to relief starts with not viewing your thoughts so judgmentally. They are just thoughts. Your mind presents them to you because it's trying to help you. The way you have reacted to the thoughts in the past has 'marked' the thought as being important. So, your mind is going to try and bring up all thoughts that are 'marked' as important over and over. The content of the distressing thought is rather unimportant. What is important is how you are reacting to them. It's difficult, but try to take a more observational viewpoint with your thoughts rather than a judgmental, analyzing approach.