Merely because of age, he will not go to jail, because 17 is the age of consent in Texas. However, until you are 18 years old, you are a minor. Your parents control you and your finances and your lifestyle until you are 18 and capable of supporting yourself.
If you want to protect this man then don't start dating him until you turn 18.
The strike of midnight on the date of your birthday you are an adult. You can immediately leave their home. They cannot do anything.
Of course, at the strike of midnight they can ask you to leave the house because they are through being legally obligated to take care of you since you are now an adult under Texas law.
You won't want to hear this but if he is 20 then he is probably just dating you because you are younger than he is and he can control you.
Beware if he already has children by other women, have been to jail, is unemployed, does not have a high school degree, takes drugs, drinks, etc.
What is his past dating history? If he has a string of past girlfriends then what makes you sooooo special. Be prepared to be another notch on his belt.
If you have sex with him, I highly recommend using contraceptives. Especially if he does not work, drink, does drugs, etc. If he has no money then you have no business having children with him.
I also recommend that you graduate from high school. It's easier now than later.
Do all of your adult relatives hate him? If so, then beware. They probably know more about life than you do.