I am a US citizen and I have known my boyfriend for 2 years. We are now currently expecting a child. He is here with a visa. How do we go about getting married?

YOU are aware... being married won't make him an American.. or even guarantee he can get a green card?

You go to the court house and get a marriage license, go to a pastor and get married

Congratulations.

Depends on what state you are in; but generally, both of you go the courthouse or county clerks office for a marriage license, you wait the required time (if any), go to a JP or Pastor and get married.