I’m 18 and I need advice about sex 😳

Hi. I’m 18 and my boyfriend is 20 and we’ve been sexually active for a little over a year. We both lost our virginities to each other and basically this is kind of awkward and embarrassing to admit but I don’t know how to be on top when we have sex. We both haven’t figured it out yet, so we just never try to have sex in that position anymore. I always thought I only had to sit on it and go up and down but comes to find out I can’t sit straight up because it hurts him. I haven’t found a comfortable way to position myself. 😳.... any advice on how to have sex in that position?