What Causes Fear Towards Sexual Life?

I want to give my introduction first.I was asthma patient(allergic to dust).So in my childhood i was not normal like other child to play around.Since i was allergic to dust and some kind of foods(especially cool items) i used to sit in the house watching tv.I didn t have friends to play with.My father is having transferable job so i never had constant relationship with anyone.Now my problem comes,it started when i was at the age of 13 or 14.I saw a movie in which there was a kissing scene which created some type of sensation in me.Actually i liked it.Then at the age of 17 i saw some another english movie in which they had some nude scene,it gave me more sensation and a type of satisfaction.Whenever i see these type of movie i feel like more satisfied and feels it as if happening with me,i crosses my leg tightly till i get some type of satisfaction.I don t understand why its happening and how.Now i am 21,my friends watch porn,which i don t like to watch.I have a boy friend, i think to make love with him but in reality i scares and run away from the situation.Whenever i watch i tries to watch porn it makes me sick,uncomfortable and depressed.I am very conservative type of girl.I feel disgusting to see me,touch me.I want relationship but not sex.Now i had problem a with my parent they want me to marry someone which i don t want.I cant able to tell this to my parent.I really don t know what to do.Is it related to my past that i was alone in my childhood?Is it psychological disorder?