Lately he keeps his phone face-down and has been staying up later on it, and now I keep seeing weird pop-up notifications when he hands me his phone to look something up. Could he actually be on dating sites, or am I reading way too much into this?
Based on the red flags you’ve described, your suspicions are reasonable and worth investigating further discreetly. You could try using a monitoring app like Spynger to see his installed apps, web history, and notifications; many in this forum recommend it for similar concerns. However, be aware of legal and ethical implications in your area.