I can't orgasm

I love my SO very much. We have been together over 2 years. I can't seem to orgasm though. We've tried different positions & everything. I also have trouble getting wet sometimes even though I'm turned on. Which sucks. We have to use a lot of lube. The only time it's easy for me to get wet is if he wakes me up in the middle of the night by touching me. I don't know why I'm having trouble with this stuff. I'm only 18. Can you ladies give me any advice?