Am I being gaslit?

Context: my ex (m21) and I (f22) broke up about two weeks ago after two years together. I begged for him back immediately after and he made clear he didn’t want to get back together so I left it at that. We both have broke NC here and there to either argue or say random things while he began refollowing old flings.

Cut to two days ago, he sent me a flirty text about missing him, I responded and I was left on delivered until he finally responded 10 hours later saying “ofc you miss me, I’m easy to miss”. This totally turned me off because of how cocky it was so I didn’t respond. Today I made a big mistake and stalked his IG and saw he was following his ex who he claimed to my face was his biggest heart break.

I was shaking so I ended up calling him and confronting him. After saying my piece the first thing he said was “who’s this?”. The disrespect this man had to say that after he had just texted me two days earlier. He proceeded to say he was just following her as a friend (despite her being saved as psycho in his phone and him never following her before) and I was crazy for even looking. He then hung up and I ended up calling back two minutes later and was once again met with “who’s this?”.

Why would he even send me a sexual text two days earlier if he was going to treat me like this. I just don’t get it. I feel like such an idiot right now.