My friend whom has a girlfriend showing jealousy signs?

So my issue is with my friend who i’ll call Carl for privacy purposes. But I’ve been friends with Carl for a while now and last year he had broken up with his girlfriend so we became close & started on the low seeing eachother. Well due to circumstances with petty ex friends he ended stuff with us but we still remained close friends/ friends with benefits. Carl got back with his girlfriend a while back and well this is gonna sound bad on my part but Carl & I have continued our sexual encounters. When they initially got back together is wasnt that often due to quarantine but now its been picking up a lot since we have moved in together as roommates. I’m not going to lie i still have some harbored feeling for him that never went away in all this time so i’ve obviously been single for a while now but i am working on it by trying to talk to other people rather than only him. Recently my ex has msged me apologizing and we’re casually talking again as friends but whenever he sees me on my phone and the imessage screen is up he always sarcastically says “oh is that your boyfriend” “by the way you’re smiling it is” stuff like that. At first i didn’t really notice it but now it’s every time im texting someone he says that even when im just texting my dad. I’m in no way hoping that he’s gonna be breaking up with her for me or any of that usual “side chick” thing. But im just curious to why the sudden jealousy or is it not & im just over thinking it.

How did you move in as roomates if he has a girlfriend? I am so confused because if I was his girlfriend he would not be moving in with another girl....even thinking about that type of living situation and relationship is making me really angry.....for personal reasons. So he sees you get messages on the phone and gets jealous...then obviously he wants all your attention....which means he likes you. And I'm not understanding why your not being honest with him and saying...its my ex? Is it because you want "Carl" to like you and if he does you won't talk to your ex? Is it you want Carl to show you that he likes you cause you like HIM more than you like your ex? But your not sure if he likes his other girlfriend better? I guess I don't know what "you" want....Do you want to be with Carl more seriously? Or, do you want to remain friends with benefits and room mates only?

Man, times have changed. But what hasn't changed is what it takes to have a loving, long term relationship with someone that means everything to you. So if Carl means everything to you, what should you do differently to be with him and only him? If you are OK with Carl being only a "friend with benefits" continue your current practices. You will always be sharing him and he will apparently being sharing you. Here is a shocker for you. There are partners (spouses) that will be totally devoted to you. Carl may be one of them, but current behaviors will have to change. Good luck.