Sex (PLEASE HELP)

My boyfriend and I have been together for almost 6 months and we’ve talked about having sex a lot (he’s 16, I’m 15). I used to have sex all the time with my ex, but my current bf is a Virgin. I never got nervous to have sex with my ex, even when I lost my virginity to him, but I’m soooooo nervous to have sex with my current bf. Every time the mood is right I get nervous and kinda make sure things don’t go any further. I really want to have sex with him, but it’s hard to because I get so nervous.

I’m basically asking how can I be less nervous in the situation and just relax and have a good time?