How do I tell my Mom and Stepdad I am in an odd friends with benefits relationship?

Not too long ago my one friend and I decided that we were going to do the friends with benefits thing. He just got out of a bad relationship, I just wanted some sex. My mother and stepfather are very hardcore Christian, and recently I got into a bunch of trouble with them for reasons I'd rather not discuss. Because they say they can't trust me now, they forced a tracking app on to my phone (Life360 - so if anyone also knows ways to bypass that without turning off your GPS, thank you). When my friend and I go to do it, I am to just go to his place, but my family doesn't know him or where he lives, they're going to ask questions, and I'd like to be able to just leave the house at night without them pestering me on where I went and flipping out because I didn't tell them where I was going. The odd part about the entire thing is that there is a sizeable age gap between me and my friend. I'm almost nineteen, he is twenty-nine. Even though they don't actually know him, they know I am friends with him and have made jokes about how I'm dating someone much older than me, yes I know the age thing is weird, I know it's not normal, but I don't care; normally I act and feel much older than what I am because I had to grow up fast. I just want to figure out the best way to let them know that will allow them to just accept it and let me be. They really can't say much because there is a nine year gap between my mom and stepfather, they also started dating when my mom was nineteen.
Answers

Serene E

They don't want to know. you're crazy.

Foofa

The only reason to tell them this is to upset them. So you might ask yourself why you're so keen to pick a fight. The reality is that if you're still living with your parents you're 18 in name only and don't have the freedom a real adult would. The trade off for the financial security you enjoy is that you'll have to curtail your social life a little bit. Considering what rent, medical insurance and housing cost these days I'd say you're still getting the best part of the deal.

D C

Make better choices! Stop being a THOT

Marie And Alan

You are indulging in sex without commitment. All he wants you for is sex. Logic demands that sex is best in a loving, stable relationship, not a hole in a corner affair

Suzy Q

You DON'T tell them. It's none of their business, and telling them would bring nothing good. By the way, it IS possible to leave the house without your phone, you know.

Patricia

Do your parents tell you all about their sex life? NO? Then why discuss yours with them.... ? It's private. And when i was 19 i dated someone who was 29.. we dated for five years. I don't see a problem. You're of age to make your own, private decisions.

Anonymous

It does not matter when they started dating. Your mom wants better for you. You're not even dating, you're f*cking some guy who only sees you as worth sex, not worth a relationship. At least your step-dad was man enough to make your mom his wife. You're stuck as just a piece of meat. You need to learn to love and respect yourself or these older "men" are going to keep using you as a sex doll.