Sertraline is very promising drug for OCD. Most common side effects in the initial period  may be gastrointestinal upset, slight sleep disturbance, anxiety but memory loss has not been reported. You might face some emotional numbness in initial few days but it will subside by about 2 week.

Obsessions can be very distressing alongiwth fear of being evaluated in social situations. I can completely understand what you are feeling. But one thing that we need to understand is that even though we may feel that this problem has altered or changed us as person forever, it has not. Trust me it's just a temporary phase like any other medical problem which will go away with treatment. We need to be stay motivated, don't over instruct your  self to forget about the thoughts or to focus on the positive as this will indirectly increase the frequency of your thoughts. Keep yourself distracted and also take professional counselling sessions for a proper plan.