Did I have the right to ground my son?

I am a single mother with 4 kids in Texas. My 17 year old goes to school out of state. He's a freshman at LSU. I watch my son consistently on life360. I can tell when he's speeding, out too late, somewhere sketchy, etc. I only do that to stop him & remind him that he's still a minor child and whatever those young adults he's around do will one day be faced with consequences. I went on my son's Instagram before this month and checked what he was tagged in. There was a picture of him looking drugged out as he laid in bed shirtless next to an also shirtless, smiling girl. So when he came back home recently, I talked about STDs and asked him if he's ever been with multiple partners (Trying to trick him into admitting he has sex.) He said only 2 but they're clean. So I told him while he's still home with me, he's grounded and no girls, parties, late nights at his college until he is a legal adult. I'm no prude, guys. Sex is something that is fun and should totally be enjoyed.. By people who are old enough to fully understand and pay for the risks.