Guy's Behavior

The guy I like calls me sexy but has a girlfriend?

My "situationship" texted me out of nowhere after almost a month of zero contact. Last week I noticed his insta had initials and a heart in his bio and a selfie with a girl and him as his profile pic. I found the girls insta and can assume it's his girlfriend (they both go to the same college). Just around 2 or 3 days ago he texted me saying, "Hey its been awhile. How have you been?" We chatted and he said he'd like to hangout soon and would love to see me. And just today he texted me "Hey sexy." I don't know if him and his girlfriend are in an open relationship or what... is he just trying to keep me as an option or trying to see of there's anything there with me? For more context i've known him since middle school but never talked to him/hanged out in the same circle as him (but i did and still have a crush on him) and we have been talking on and off for almost 2 years now. So should I cut communication with him or what?

Updates
+1 y
UPDATE: i made a fake instagram account and messaged his girlfriend. i found out he is not in an open relationship. yesterday i sent his girlfriend the proof of him cheating and right after that i noticed he blocked me on snapchat and instagram. she told me that he said this happened in his previous relationship (a girl sending his girlfriend screenshots of messages that he's cheating). she told me they have been dating since October, and thank you for sending her the message.
The guy I like calls me sexy but has a girlfriend?
Post Opinion