I dont know how to orgasm and my boyfriend is getting worried

[Confused]

So i met my boyfriend several months ago, our relationship moved fast and hard, and i cant imagine lossing him now. Well three months ago i lost my virginity to him (im a 19yr old if that helps im aslo bi-sexual and demi-sexual which means im not sexually attracted to anyone until ive formed a deep emotional connection to him/her ) and since then we've basically fucked like rabbits. Because of our hectic work schedules I only get to see him on the weekends most of the time but he spend the nights on friday and Saturday when our schedules alow it and we'll get busy 3-4 times a day. But ive never bern able to orgasm. Recently hes been acting a little discouraged and worried afterwards and when i asked what was wrong he says hes worried that hes not good enough or that I'll think hes just using me for sex, im not his first by far and he said its never taken this long for him to get a girl off. What should i do? Any hints, tips or tricks? Or even an explanation as to why i cant?