Well, since you didn't answer my initial questions, it's a bit harder to know how to answer these.
But a partner who has unprotected sex yet never considers a possible pregnancy isn't exactly the greatest vote of confidence. And it's unsurprising that your father doesn't want you seeing this guy, especially if there are also other troubling factors in the mix like, for instance, if he's notably older than you are.
Had you yhet told him when contact was cut off? if so, how did that discussion go? Has he SAID he wants to be involved? You wanting him to doesn't mean he will be: the only real legal power you have is in obtaining child support funds, not co-parenting.
What I might suggest is asking your father is this guy can come to your house, is a supervised meeting between all of you to discuss this. Given your age and the fact that your folks are likely going to be the people who bear the most responsibility here, after you, and likely will trake care of a lot of financial and practical stuff, it's not invalid or out of line from them/him to be angry, to want to set firm limits.