I’m in an ldr. my boyfriend is frequently online on whatsapp more than he is on other apps. what does this mean?

Hi, so I’ve been with this guy for almost 2 years now. We haven’t met in person yet but plan to close the distance soon. I’m just noticing this recently that he is constantly online on Whatsapp. Even while at work, he would go online but not respond to my messages. I know that they have a work groupchat but in general his job does not require him to use Whatsapp at all. Everytime we talk on the phone, he seems distracted, I would keep our whatsapp conversation open and notice that he would go & off whatsapp, he’s distracted at times too (as if reading or responding to messages). We don’t always do videocall (maybe twice a week) but when we do, he always seems distracted as well (like he’s reading the notifications - and i noticed that he’s constantly getting notifications too, based on his eye movements).

I know this sounds stalker-y & unhealthy, but I just need my feelings to be validated. Am I crazy? Should I talk to him about it? How should I go about asking him without coming off or sounding crazy?

Updates
+1 y
update: i asked him very gently if he is/has been talking to other girls but he said “No,” and he sounded sincere. but i was scared to mention the whatsapp thing, and it’s still bothering me and i’m scared to bring the “are you talking to other girls” issue again :( i think i messed up my chance lol
I’m in an ldr. my boyfriend is frequently online on whatsapp more than he is on other apps. what does this mean?
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