No,Im sorry,I disagree. Marriage is a commitment before God and it is important. Sleeping with someone doesn't magically make you married. It takes work, commitment and maturity. Just not good advice at all.
To the OP you now have made a decision that will effect the rest of your life.You're a father. I hope you take that commitment very seriously because God does. As far as marriage you are very young. My advice would be that you both begin counseling either by your pastor or a Christian counselor before you take the step of marriage. You're both very immature and you're going to have to grow up quickly. Surround yourself with good strong adults and learn as much as you can about parenting. You are now taking on adult responsibilities. Be very careful of the decisions you make.Your child is counting on you.