Waiting it out..

So I'm 15 almost 16 and since I was younger I knew I wanted to wait until I'm married to have sex. My boyfriend is 16 and we have known each other forever, best friends for life we just finally started dating almost four months ago after knowing since we were little that we are into each other. I still want to wait and he respects that and doesn't mind but at the same time when things get a little "heated" I feel like I can't stop, but I do. What should I do.... Would anyone like to share their experiences with me or advice, would be greatly appreciated