Relationship problem...

lolno
Just four months? It just already started. He's already sending red flags. Get out of there when you have the chance.
I highly doubt he has the money, the job, the responsibilities, and the mindset to become a father already. Fatherhood is serious. You're also probably too young to become a mother.

In a relationship there should be mutual respect and understanding for ones feelings. If he is trying to pressure you into things and then acting childish after you refuse then it isn't worth it.
You deserve someone who will move through a relationship with you at a speed that is comfortable with the both of you.
I would try to talk it out first before you go and break it off. Although if he keeps asking you like you say he is then I doubt he would consider going at a slower pace, but you don't know unless you try ~
I hope you feel better and i hope this helped a little.