If you really care about yourself and having a good long-term relationship someday, you won't have sex at such an early age -- especially not with the boyfriend you've described. It may seem as though nearly every guy and girl in your high school is having sex. First, that's not even close to being true, and second, none of that will matter to you or anyone else in a few years. You're not hearing about the ones who are choosing to wait, but with this boyfriend's way of talking about his ex-girlfriends, my guess is that soon after you have sex with him other people in your HS will know about YOU. If your reputation and sense of self-respect matter to you, don't take that course.
Also, I know the excitement of dating a guy is overwhelming right now, but as other responders mentioned, an STD or a pregnancy could seriously damage plans for marriage, college, and so on, depending on how bad it is. A huge percentage of teens who are having sex are getting STDs because they are sleeping with other teens who've already had many partners. Just because you take a pill or use a condom does not guarantee your safety. There is no safe sex except when you're in a loving relationship with a person who is mature and responsible, and would never harm you by exposing you to those risks. Does this boyfriend -- who disrespects his ex by talking about her that way -- sound like the type?
I hate to lecture you, but it sounds like you need some more serious advice than some of the other responders gave you. What you now see as mostly fun and adventurous will be more important to you some day. And despite what you may think about guys, many men really care about dating and marrying women who were responsible at a young age. Please don't put your health or future at risk to please some guy you'll never see after high school. Think about what you owe to yourself.