Teens; Would you tell your mom if you thought your dad was up too something?

Well I woke up really early this morning and I was working on my puzzle(ha I know what a loser!) But anyways my dad was like you should go try to go back to sleep so I went to my room. I few minutes later I could hear noise coming from the computer out of the living room, it was moaning. So I opened my door to peek out there, and my dad was in his under wear (He was in his shorts, a couple of minutes before this) He then put his shorts back on and came to talk to me, he was like you look like your about to cry and i was like uh no dad im trying to go back to sleep, and he was like whats wrong. I was like I am going back to sleep, and he was like alright. I'm pretty sure he was watching/looking at porn. Should I tell my mom? I Don't wanna be around my dad anymore..