Well, you are still young, but it seems to me that you have a lot "catching up" to do regarding maturity. I was in high school not too long ago, so I understand how some guys want to have sex, but I also know that they do not simply go up to a random that doesn't seem to want sex just to ask to prom... for sex. I hope that you understand what I have written up to this point. I am not suggesting that you "gave him mixed signals", but what I am thinking is that you were not really "firm" when you told him no. Now, I am not saying that what he did was "right", but it would be stupid to expect teenage boys to be "ethical". So, what I am telling you is that: yes, what he did was wrong. It was wrong of him to try and impose himself on you like that after you declined his advances several times. But, I am certain that you were either subtly flirty or submissive to him. It had to be one of those two in my opinion. That is because he was asking you to prom (for sex) which is just something he wouldn't have done if you had given a firm and "cold" no. I mean, the way you apparently told him :"I really don't appreciate being talked to like that" seems to indicate that you were trying to reason with this guy. You were trying to get him to understand your feelings. And that is where you went wrong in my opinion. And again, I am not saying that what he did was okay- it was wrong, bad, and maybe even mean- but he wouldn't have been so persistent if you had been more firm in your "no". Trying to dialogue with him -trying to get him to understand your feelings- was obviously not that effective. You could have simply told him something like "If you don't get away from me, I will take this to the principal because it is sexual harassment". I can assure you, he would not have kept on asking you to go prom after that.

Secondly, I really do not mean to blame you for any of this since you are still young and still learning, but you messed up in lying to your mom in the first place. By telling her about what the boy was doing minus the actual "bad part" about it, you gave her faulty information to work with. And therefore, of course she was going to give you faulty advice. But then, when you told her the actual truth, she had two choices in her mind: 1) to accept that you were telling the truth "now" and that she had been fooled before-or- 2) That you were lying "now", that she was smart enough to "catch you lying", and that she had been smart enough to believe you in the first place when you were telling the "truth". Which of those choices do you think was better for her? So, of course she took the second choice in this case, because the first one seemed to imply that she was fooled in the first place, and the second one seemed to suggest that she was smart and "on top of it". Anyways, I don't know what type of family situation you are in, but if your 16th birthday part was going to be your first Birthday party, then it seems to me that your mother probably isn't all that kind or wise. I don't know, but I just get the feeling that she is not a very affectionate mother. And that is her fault, not yours. The children do make the parents, the parents make the children.

So, I think that you have a bit of maturing to do, and you should probably learn to be more assertive and more independent in your decisions.