I am 21 years old. I had my first sex when I was 20 years old. Before that I never tried masturbating or inserting anything in my vagina. During my first sex it hurt a lot when my boyfriend tried to penetrate. It hurt so much that he could not penetrate. For the next one year whenever we tried to have sex  he could not penetrate because it hurt a lot. One time he actually got to penetrate but it bleed a lot but after examining (by ourselves) we came to know that it wasn't due to hymen tear. It bleed because of the small opening of my vagina and there was kind of a skin tear at the opening of the vagina. my boyfriend thinks that my vagina opening is very small and regular sex can solve this problem ( we are in a long distance relationship so we don't  have regular sex,there is a minimum gap of 3 months in our sex life). 

It actually pains a lot.. so basically neither of us can enjoy sex. It hurts only at the opening and is really unbearable. I am quite tensed. Can you please tell why it hurts??And what should be done???