I keep having sexual thoughts about my boyfriend, we're both virgins and I'm really scared about having sex for the first time but at the same time I really want to. He says he wants to wait until I'm completely ready, but these thoughts are really tempting. What should I do?

How old are you. Having thoughts is one thing, most people do, Actually having sex is another is should only be done when you are ready to become a parent.

Are you out of high school at least ?
Do you and /or the boyfriend have a job to support a baby?
Are you even old enough to legally have sex or would it be a crime for your boyfriend to have sex with you?

How old are you both. Thoughts are normal between partners. Actions should be a lot more thought out. They have lasting consequences.

The whole "Are you ready to have a kid?" argument I've never exactly agreed with. Lets me restate, I agree with it if we were in a perfect world. However, most people are not going to pay attention to that. I know if somebody told me "Are you ready to be a parent?" before I had sex I wouldn't take it very seriously. Because, facts are... we are young and naïve when we are first thinking about having sex. So, instead I suggest an alternative. If you are thinking about having sex, I would highly suggest that you go on birth control right away and you are emotionally ready to have sex. Make your partner wears a condom, because being double protected always gives extra security.

Hard to really advise an OP without knowing her age.