I have two teenagers, a daughter who just turned 16 and a son who is 17. When I was growing up, my mother and I didn't have that "bond" >>> we didn't talk, didn't discuss things, and what I did learn was on my own... basically my mom and I weren't close at all. I swore when I became a parent, I would be very open minded with my children, non-judgemental and absolutely nothing/no topic would be taboo. Being mom and dad (since their father died several years ago), I have had the "talk" with my kids when they started showing an interest in the opposite sex. At first, they were embarrassed to talk to mom, but over time, they knew not to be ashamed or embarrassed. You have to be persistant, and most important, non-judgemental. I know it is difficult to even think of our children having sex... but it will happen eventually. You have to make sure they are informed...they are educated on consequences.... and to protect themselves from disease and also pregnancy. I have told both my teenagers to always use condoms when and if they do have sex, not just for my son, but also my daughter. (I bought each a pack of condoms just in case) That is the next surest way to not obtain a disease besides abstinance. And I do preach abstinance!
About stopping your daughter from seeing this boy.... what I did with my daughter, was tell her to invite this boy over to our house for dinner, watch a movie, play scrabble, etc. I also do make a point of speaking to the parents and meeting them if I can. I am old fashioned in a way, meeting the boy or the girl (in my sons case)... I believe when this happens, it does garner some respect towards the parent and to their "love" interest and they might think twice. If there is no respect, hopefully, your daughter will sense this and stop seeing him. Use some psychology...hehe. I tell my kids, I'm not going to stop you from seeing him, but he (or she) has to come over to the house so I can meet him or her. And this way, they are closely monitored.
About birth control... I know that most people will think if a girl is on oral contraceptives it means they are sexually active and it gives a negative stigmata towards the girl. And in some cases placing your daughter on birth control gives her the go ahead to have sex. Not so... in my feminist views that I tell both my children... use CONDOMS... I stress condoms more than anything. Both men and women need to be equally responsible for preventing pregnancy and disease. And they need to be informed of the consequences if God forbid, something should happen. You know the saying, it takes two. Also, oral contraceptives has some benefits... such as, reducing acne, less cramping, more regular, shorter periods... stress the importance of these instead of preventing pregnancy. To go on oral contraceptives, you will need to take your daughter to the doctor or to a clinic to get a prescription. Also, please keep in mind, that your daughter can go to a clinic on her own and obtain birth control without your knowledge.
Also tell your daughter, that you were her age once, and that you know more than she may think. You don't necessarily have to tell her you know she is having sex. I know that most teenagers believe the world revolves around them and they don't think anything can happen to them. Inform her, educate her, give her your wisdom of what you went through at her age without giving her specifics.
I know I am very open-minded and a lot of people do disagree with my views and the openness I have with my kids. Just talk to your child/children and also listen, don't just lecture, don't get angry, be supportive, be understanding and give them a chance and listen to what they have to say without getting upset or judgemental. I am reassured with myself that I have a great relationship with my children, and I hope you will too.