[21M][21F] Together ~11 months — feeling uneasy about girlfriend’s online activity, am I overthinking?

I’m 21M and my girlfriend is 21F. We’ve been together for around 11 months and haven’t had trust issues before, but recently I’ve started feeling uneasy and I’m not sure whether I’m overthinking or if something is genuinely off.

Over the last couple of months I’ve noticed some things that make me uncomfortable. For example, when we’re together I sometimes see messages from other men on her Snapchat — usually opened and not replied to, but occasionally I can tell she has replied (I don’t see the content, just that she has). I’ve also noticed her liking a few guys’ photos on Instagram/Facebook during our relationship. None of this is concrete proof of anything, but combined it makes me feel insecure and unsettled.

She has also been a bit less affectionate and emotionally available lately, which could just be the honeymoon phase fading — but alongside the above, it adds to the uneasy feeling.

The main thing that’s bothering me is this: we used to FaceTime until we fell asleep. Recently she’s started ending the call saying she’s going to sleep — which is fine — but then I’ll see her active on Snapchat at 1–3am. When I brought this up calmly, she said Snapchat sometimes shows her as active when she isn’t, but from my experience that hasn’t really been the case. This makes me feel like she may not be being fully honest, and that’s what’s troubling me more than the app activity itself.

I’m trying to figure out: Am I reading too much into normal behaviour because of my own insecurities?

Or is this something reasonable to be concerned about and bring up again?

I don’t want to be controlling or accusatory, but I also don’t want to ignore something that’s genuinely affecting my trust and peace of mind.

How would you suggest handling this situation in a healthy way?

TL;DR: My girlfriend has been less affectionate and active on Snapchat late at night after saying she’s going to sleep. I feel uneasy and don’t know if I’m overthinking or if I should address it again.