This is perfectly normal. Most women are like that. When we, men, are 18, it's okay, we're glad to get to have sex. When we reach our 20s and 30s, we will think back of you as a really bad sex partner. In my personal experience, woman start to become interesting in bed from like age 25-27 and above. And as a young men it's very boring to bang "dead" women in bed but that's the best you can have so you take it. Now, it's up to you if you want to be a bad memory in your boyfriend's mind 15 years from now or not. You are exactly like my one girlfriend was when we were in the 25-26 range. Worst sex partner i've had (in a relationship). Having sex with a girl who doesn't seem enthusiastic about it feels like you're raping someone (without the violence part). The point is that young people don't have perspective. You will be an okay memory today but as the years go by and better (and worse) experiences accumulate, you will become worse and worse memory (in comparison).