I must say that as a mother of 3 teenage sons, this is a difficult thing to deal with. My oldest son was sexually active at 14. Me and his dad spoke with him in depth about the 'big picture' of this decsion. We provided him with condoms, told him of the diseases, pregnancy and possible child support that could result in continuing.
I always haved an open door with my sons to me to talk about anything they want . I may not always want to hear what they are saying but i feel it's important to have open, honest communication with them.
As far as them being sexually active, I certainly didn't want to encourage it, but i could pretend it wasn't going to happen or ignore it OR I could be pro active and help them make responsible decisions.
The whole JW attitude toward sex is repressive, unhealthy and abnormal. You can teach your son how to be responsible and make good choices if you continue to talk to him.