<human>: We've been dating for over a year now. She's never been amazing at texting or anything like that, but we've always had fun when we have been together. 

Recently, she has been very distant. When I have texted her at night, she has not responded, telling me that she was "having a bath" and didn't want to wake me when she got out, or fell asleep early. I never looked too far into this, until last night. 

I was talking to a friend of mine on what's app, approximately an hour after the last received message from my gf, including me sending a "goodnight, love you" type message, and accidentally clicked my gf's name instead of my other friend. 

I was shocked to find that she had been active just 5 minutes before I clicked her name. So basically, she was ignoring my texts, and just telling me she went to sleep early.

I know she texts other guys, that's never bothered me because she's never made me feel insecure about our relationship, but this is different. I am ashamed to admit that I kept checking, and sure enough she consistently opened up what's app for another 2 hours after that. It's not that she's texting someone else that bothers me, but that she couldn't even bother to message me back, and she is messaging whoever this person/people is until late hours of the night.

How should I approach her about this without seeming like I've been stalking her? Is this all in my head and I'm just overreacting?

Could you distill the essence of the text into 1-3 sentences?
<bot>: my girlfriend of over a year has been acting distant and is not responding to my messages. I found out that she has been texting people for hours after she pretends to go to sleep.