Is he cheating?

[u/NoRepair7302]

TL; dr My boyfriend (M21) and I (F21) got back in touch after 3 years. Three years ago, what we had was more of a situationship. After all this time, he texted me just to ask how I was doing, where I was, and what had changed in my life. I told him that 2.5 years ago I left the country and I don't know if I'll ever go back. We had amazing conversations and talked on the phone for hours.
Two weeks after we "reconnected," I got a message early one morning saying he didn't want to keep talking to me, that he didn't know if we'd see each other in the next few years, and that the huge distance and time difference were weighing on him. I stayed silent all day and only wrote back many hours later, after working up the courage with a few glasses of wine. I told him everything: why I hadn't had a relationship in 3.5 years, that I loved him, that I'd been waiting this whole time and hoping so badly he'd write. I'd spent those years on a tiny bit of hope, on a man who was in a relationship the entire time. Two weeks later he wrote again and wanted to apologize for being impulsive. Everything was wonderful again, and for the first time in my life I told someone I loved them. I'm a pretty dry texter and a fairly cold person, but after saying "I love you," I discovered my affectionate, tender side for the first time.
Then everything changed in a single day. He went away for a week to relax with his friends. We sent our usual "good night, I love you," and I went to bed. By midday my time it was already morning for him, and he always texted me then. That day the hours kept passing, and it was already evening for him, so I wrote first. His replies were dry, and he didn't ask anything back, not even "how was your day?" I had an important meeting that day that I'd prepared for a long time. He knew, but didn't ask about it at all. I started looking for the problem in myself, but everything was perfect the day before, and my conscience is clear: I've never cheated on him, never sent mixed signals to other guys, never gone on dates. I asked him several times what was wrong. His replies take hours, when he normally answers fast. And it's always the same: "everything's fine, I just need to sort out some personal stuff" or "I'm really busy these days." When I ask what stuff, there's no answer.
You might think maybe something happened with his health or his family, but we were at a point where we told each other everything and shared our problems. So I started wondering: what if he ran into his ex again, or met someone new? I checked who he follows, and there really is a new girl I don't know. But I don't know his ex either, so I can't tell who she is. Still, the fact is he followed someone new.
I don't want to be jealous, and it makes me so angry that this is stealing my peace, that I can't sleep at night, that I'm stalking his follows, that all these thoughts keep creeping into my head. What would you do in my place?

[u/alluringdefection]

Girl went from love bombing to ghost mode in the span of a week trip, the new follow is just the cherry on top.