really feel like talking about this

Hey everyone! I haven't been here in a pretty long time, so I suppose most don't know me. But something happened last night that I felt like talking to someone who might understand, and since I don't really have any friends left, I thought I'd just post it here. Maybe someone will answer, maybe not, but at least I can get it off my chest this way.
So here goes:

The background story is, in short, that I was with a guy on and off for three years and ended the relationship once and for all about 2 and a half years ago. The crazy thing is that it was just an online relationship, we were at one point thinking of getting married one day, but we never actually met face to face.
Anyways, after I ended it I completely ignored him, blocked him on social media etc. and everything was fine until recently I logged back into facebook after not having been on that site for a long time, and I realized he had been messaging me there the whole time, until May this year. I blocked him on all profiles that I knew for sure were his, but there was also a girl I had talked to a while back who sent me a message (I've never met her in person either) so I started talking to her on facebook.

So this is where it gets weird. I was talking to her for a few days, and it seemed to become clearer and clearer to me that she was really my ex, pretending to be someone else. I had several reasons to suspect this (like personality, calling me a nickname only my ex ever called me) and I called him out on this last night. Of course he/she denied it, but I ended up blocking him/her. What made me even more sure it was him was the way he/she reacted when I told her/him what I suspected. You'd think that if she was legit, she'd call me crazy and get out of there. But he/she didn't even really seem surprised. Just calmly denied it.

The reason this is bothering me so much is that I will never know whether I was right or not. I can't prove or disprove it. I know it shouldn't matter, I've long moved on, but for some reason... I think I just don't want to admit I might have just been paranoid. If I could prove that it was him trying to weasel his way back into my life, then I would seem saner. I haven't told this to anyone, because I know everyone would just think I'm crazy. That's why I'm posting this here.

Anyways, good to get this out, I guess. And thanks for reading, if you did.

Chances are, after all that time of talking with him, your hunch is right and you're not paranoid. You'd know what he's like and how he'd say things, particular phrases he'd use, grammar (would he use capitals? Punctuation?), etc. People can try to impersonate someone else, but over time, and especially in on-the-fly print, they will quite often slip up and interject their own personality back into it.

Of course, there's always a slight chance that it's just a freak coincidence, but it's unlikely. If the magic 8-ball in your head keeps saying "all signs point to YES", then more often than not, it's correct.