Personally I don't think him saying "I love you" only after sex is necessarily a bad thing - in my mind, it is probably because you two just did something very intimate, and he feels that it is perfect timing to say it then. Like one poster mentioned, he probably doesn't even realize it. If he said "I love you" and stuff like that before you guys even ever had sex, then I'm sure his feelings are true. If he was only using you for sex, I don't think he would continue a b/f g/f relationship with you when there are many girls out there these days who would welcome casual sex any time an offer rises (meaning I think your boyfriend could find sex anywhere if that is all he wanted from a girl). However, no matter what, if it bothers you, you have every right to state your feelings to him. Just don't be harsh or anything because most likely he has no idea he only says it then - and he will probably feel bad knowing that it bothers you. Someone suggested saying I love you randomly and see what he says. That's a good idea. I'm sure you'll find that he was clueless as to only saying it then, and you'll find him saying it much more

Take care and let us know how it goes!