<human>: Summarize the given text in a few sentences.

Hi guys, so like the title says I [18M] have a sneaky suspicion that my girlfriend [19F] slept round her ex-boyfriend's house last night and I'm not quite sure how to go about this... 

The story goes like this. I have recently gone back to university after the Christmas break, so me and my SO have been speaking on the phone quite a bit (usually every night for half and hour to an hour).

Last night we had an arrangement to call at around 11, before we go to bed. So yesterday her day consisted of catching up with some friends, one of these includes her ex-boyfriend. At 11, after not speaking to her all day I was expecting a phone call. Time passes and she still hasn't called or texted, so midnight passes and I text her asking her how things are going. She replies about 10 minutes later saying how she just got home, but couldn't call me as her mum was in bed, etc. However, this normally isn't a problem for her as she'll go downstairs to talk to me... But after texting her to ask how her night went she didn't reply. This morning she texts me saying sorry and that she simply fell asleep.

After being cheated on in the past I have quite bad trust issues and for some reason I don't believe that she actually went home last night. My question is how do I go about this? Am I overreacting due to past experiences or do I have the right to question her about where she was last night?
<bot>: I have a sneaky suspicion that my girlfriend is hiding something due to weird activity on her behalf, how do I go about this? confront her or trust her word? Need some advice please!