can't hold off on sex

So I am talking to/dating this guy. We've been talking for almost a month and right away I told him I wanted to hold off on sex. He agreed and didn't push me for more. But when we're together I can't help but to start things and we ended up having sex because things were getting heated. I was the one to start it, he wasn't pushing me. Is there something wrong with me that I can't control myself? This has happened before, I never seem to have control. Do you have any suggestions that might help me?:/