He likes to watch threesomes? Help?

So do I need to be okay with this? I was okwith him watching porn but for some reason threesomes make me uncomfortable. Maybe about a year ago my bf told me while drinking that it was a fantasy of his to have a threesome with him and me and another girl, i decided to let it go because I knew he was drinking. But now i cant help putting the pieces together since he showed me the videos he likes to watch. He says it’s just porn so i shouldn’t worry. Can someone help calm my nerves a little bit? Also, he lied about watching porn at all for the longest time, which I didn’t understand at first because I told him it was okay, but I was uncomfortable with him watching threesomes so now I understand why he lied to me, I was hurt so I’m sure that’s why he lied about it.