Self - pleasuring and Hinduis, sometimes I think that I have done something wrong, that this is a sin

Hello ...i am a girl of 16 and I masturbate very rarely and I masturbate by watching sex scenes in movies ...sometimes I think that I have done something wrong and I will get a punishment from god .for e.g I have already done my exams ...an exam that is very important in my life and now I am waiting for my results and I wanted to masturbate so I watched sex scenes ...after that I thought that I did a sin by watching that and I have asked for forgiveness to god .what I am thinking is that I did masturbate by watching all these things and as I think that god.will punish me by making me get a bad result of my exam .i am suffering inside by thinking of that.the question is ''is my thinking correct?'' I pray to godess durga and I consider her to be my bestest friend in my life ...its not that I have began to masturbate but I was doing that for quite years and I got such results that was not that good and started thinking that I got that bad results because I masturbated ...its not that I failed but just a result that I did not expect to get...i prayed a lot to godess durga saraswati and mother mary just to get the results that I really want ...i prayed with full faith sincerity and a clear heart ...i dnt want to fail or get bad results ''is it a sin to watch sex scenes to masturbate though I prayed to god to get good results?''if it is a sin ...will I be punish by getting a bad result or fail and how can I atone for my sins ? Before masturbating I made a research if hinduism accepts masturbation and it was yes ..it is toally acceptable in hinduism.i really need ur advice dear friends plz help me to get out of this thinking. I have full faith in my god .may god bless u all.