How do I convince my dad to let me have sex again?

I promised my dad over a month ago that I would stop having sex with my girlfriend after coming clean to him and my mother. Now, my older girlfriend (I am 16 she is 17) is BEGGING me to continue and frankly I really want it too. I mean I know how he feels. He says he wants what is best for me, and I know that I guess I am a little young to get into this stuff. But I have thought about it and I mean we were using two ******* types of protection. We are not going to have a child...and if we do she is honestly the girl I want to spend the rest of my life with anyway, and I would embrace it (parents would be pissed, and it would not be ideal), but its not like, realistically, that would happen! Anyway...my girlfriend has been begging me to go back on my word and **** her, and I am honestly worried that I will loose control and do so somewhere inappropriate instead of prescheduled and in a private location like before. How am I supposed to convince my dad to let us be us again, before I just say **** it and have sex with her anyway (he has been really stubborn with it).