Ok- so I'll try to be transparent on both sides. My boyfriend and I have been together 4 months. He's 29. I'm 28. 

He has a best friend from high school who he talks to frequently on Snapchat (not through text or Facebook; only snap chat, where messages are deleted right away). 

We were laying in bed around midnight, two months ago,, and he got a snap from her where she was drunk at a bar asking him to come out. He replied that he was already in bed, but he would another time.

He then went on to explain that she was his high school friend. I asked if she knew he had a girlfriend- he said no. 

I tried to sleep it off, but the next day I brought up that it upset me that a random girl was trying to get him to go out drinking and he didn't tell her he had a girlfriend. He told me I was overreacting, and I dropped it.

Two weeks later, she shows up on Snapchat again asking him to hang out. I end up getting emotional and upset, because this is starting to look like a red flag. He tells me he hasn't told her that he has a girlfriend, because they don't talk that much. I'm, once again, overreacting. I try to let it go- but my gut is telling me there's something wrong.

Two weeks later he brings her up and I explain it makes me uncomfortable and I don't want to hear about her. (Petty- yes).

So the next weekend (this weekend right now) she's on his Snapchat constantly. Every time his phone goes off- it's her. Late at night, first thing in the morning- her. She still does not know he has a girlfriend and I'm still extremely uncomfortable with the whole thing. I keep trying to shake the gut feeling that something bad is happening, but I'm not succeeding at that.

Trying SO damn hard to hide my crazy, but he has no idea how fucking invalidated and unheard I feel. I'm OBSESSING and splitting in rapid cycle; desperately trying to hold on.