T.F.
I have a 17 yr old and she's had a steady bf for 13 months now. He is 18 and a Senior, she is a Junior, both at different schools.
You cannot have too much communication. Let her know your fears and your expectations. TALk about everything. I get the "oh mmoooooommmm when she reminds me that she is not having sex but I still casually mention... "a baby is lovely but it sure would throw a wrench in your plans". Her plans are a great college and studying in Italy.
You don't want them going behind your back. You say he is a good kid... I know it is hard to let go but we have to do it... so at least have part of it on your terms.
Our daughter's bf is at our house a lot. That is ok with me, I know what they are doing. He has dinner with us almost nightly. they are both here with friends a lot as well. They grow up very fast!!