He lies about friends on Facebook. Women whom he says he went to school with are strangers that he has been talking dirty to. It seems you already have your answer that something untoward is happening. If he is talking dirty to strangers online, then he is up to something deceitful. At this point, you need to determine what you are going to do about it and if this relationship can be repaired.
Last year, I caught my husband on a dating site - actually, it was a swingers' or 'lifestyle' site. At the time, we were recently engaged and I thought very happy. He'd also arranged hookups. He reacted angrily at first, almost blaming me, but was later very remorseful. I tried to believe him at the time and as there were no other issues in the relationship, we decided to stay together.
Are you scared that he might be going behind your back and you're trying to catch him red-handed and by finding his actual account on these sites? To get straight to the point, the most reliable tool is to use something like this click to check it out. With this tool you simply enter his name, and the city where you live you can also enter his email if you know it - although this is optional.
The only problem is that you recently found out that throughout your whole relationship your partner has been on dating websites, swiping here, liking there, favoriting here, and emailing here and there with other people of the opposite sex. This is a very tough predicament for both people in the relationship. The fact of the matter is that the reason is irrelevant. When someone is in an exclusive relationship, it goes without saying that being in an online dating website or app is wrong, and inappropriate.