Should the guy that got you pregnant know?

That is up to you. If you plan to have a relationship, certainly he should, even if you plan to end the pregnancy (which is your choice, not his).

Otherwise, it depends on whether or not you plan to file for support or want him to be a part of your child's life. This is a legal and moral issue that we cannot advise you on, beyond suggesting that you give some serious thought to your and your child's future.