Never had an orgasm

So I'm 16 and I've had sex with my girlfriend a couple of times, but I've never had an orgasm. Half the time, I didn't even feel that turned on, like it felt nice, I didn't feel uncomfortable or forced into it or anything like that, but it just didn't feel as stimulating as I thought it would? And I've tried fingering myself too, but I can never make myself feel sexy, and I don't really know what I'm doing, so I've never orgasmed from that either. Is it normal to take a while to figure out what turns you on or how to make yourself come? I just feel like I'm doing something wrong, or like I'm not good enough.