Do you find yourself anxious at the point of actual intercourse? It sounds like sex was a very unwanted, unpleasant experience for you at the first. That is compounded by the feeling you "had to do it for my boyfriend's sake," which should never be the case. When you are in a committed relationship (i.e. marriage), the intimacy of sex build the bond between you and your partner. If you are anxious because you don't feel anything, or haven't felt anything before that was pleasurable, you will not likely feel anything pleasurable about it.
That being said, painful sex is often a symptom of a physical or psychological problem. You may want to discuss this with your gynocologist.
I am a 20year old girl, i had my first intercourse at the age of 18 but i never wanted it, at the same time i had to do it for my boyfriend's sake. I have no serious interest in sex, i do not even get horny at all but whenever i have sex i always find it painful instead of pleasure ..now am so interested but i always feel nothing but pain when having sex......what can i do?
You have given too little information to even begin guessing what might be going on.