My daughter is thinking about having sex

So my daughter is 15 and her boyfriend is when she first got with him I didnt approve because hes older and you know what old boys want.. anyway she brought him round and he was really nice and a gentleman he held the door open for her and pulls out a chair when was wants to sit down at the table and when shes on her period he will get her chocolate and a heat pad for her.. any way I have had the talk with her and she is on birth control but I know she hasn't had sex yet but the other day she came up to me and said shes ready. I really didnt know what to do I was in shock.. so I said are you sure about this you can never get these moments back and dont let anyone focus you. She said no one forcing her its totally her choice but I just dont know how to feel.. in my house they are not allowed to be alone with each other and they are not allowed in her bedroom but round his i know they are allowed in his bedroom and his parents both work the nights shifts they both work at a hospital to 7 at night till 7 in the morning.. so they have alot of free time with each other she asked to stay round his. I said no then a couple of days later she asked to stay round her best friend house. Thinking nothing of it I said yes. Found out a couple of days later she actually slept round his house.. I grounded her for a week. But now I'm thinking what if she has already had sex what if she done it that night. I hope shes been taking her birth control pills what do I do should I talk to her and I haven't even told her dad yet I need help