The answer to your question is "Yes" it was bad for an 18 year old man to guilt trip you into doing sexual things that you did not want you to do. He was taking advantage of you and using your body to satisfy his own needs and did not consider your feelings at all.
As a young teenager, I presume that at that time you were afraid that he would dump you should you not give him what he wanted.
You have learned by this and now that you are older and wiser, you will not allow any one to guilt trip you to do what you do not want to do. Beware of wolves in sheeps clothing.
Two very young people. The boy wants something the girl doesn't really want to give. But give it she does. They both have free will and bad judgment. But where is the abuse?
If that happened when you were 16 I'm assuming you are older now, and you should know that that is bad and abuse and shouldn't have to ask. All he cared about was your body and I hope you don't let any man treat you that way again. Good luck.
oh ok thank you @RockRose
Great that you have matured beyond doing what a boyfriend wants you to do, jeni. It's a maturing process. When you're young and immature you might be more willing to do what someone tells you to do, and then with intelligence you grow past that and stop doing what you don't want to do in a relationship. But yes, to answer your question, "it's bad" when young girls are too immature to know they don't have to do what a boyfriend asks.
oh ok thank you and i did dump him
It at the very least shows he is/was not respectful or considerate of you and your feelings. It shows he thought you were something to manipulate and dominate, something that he could simply bend to his will. No true feelings were shown. I think by that (not-so-)subliminal message, it is at the very least emotional abuse. I'd dump someone who treated me that way.