This is terrible and you are going to absolutely traumatize Kate. I can hundred percent guarantee that this relationship will not last. You are very young and if you get pregnant you are basically going to be tied to him forever and that is going to be devastating especially with the age gap. You're also going to be the leading cause between Kate and her father's relationship falling apart. I can guarantee that Kate is not going to speak to either one of you for what has happened and she's going to hold him responsible and hold you responsible. You're literally being taken advantage of, but you have to take responsibility and be a decent person as well. I cannot believe you would do this to your so-called best friend and if I ever had a quote on quote best friend like this I throw them in the garbage. You are extremely selfish and you do not care about how Kate would feel about this at all. You've been a terrible best friend. And I believe people will always reap what they sow, so if you go through with this foolishness best believe it's going to come back to bite 10 times harder.