Can you get pregnant if a guys comes in you?

Yes, for sure. That is the way people have almost always done it. If you both are fertile and if it is the right time with respect to your ovulation - you'll have a very good chance of becoming pregnant. If you don't want to be pregnant, don't do that without protection. Seek information from a reliable source about human sexuality and procreation. It's important to know about what you are doing. Best!