Me and my gf have been together for a year and a half now. So I recently went to sleep over at my girlfriend's place and I noticed a beanie on her couch, one I've never seen before and I asked her about it, she told me that she thought it was mine and that she found it off the ground but not once have I left a hat at her place, I told her that it wasn't mine and she said that if it's not mine she doesn't know who's it is, she has been living in this place for about 4 months now and I've gone to hers quite often, I've never seen this once keep that in mind. She suggested that it was maybe someone that used to live there before her's beanie but there's no way that's true.

When I initially asked where she had found it she said she found it under the couch, then she said she found it on the floor next to it and then under the bed (the bed and couch are connected). Which was very weird to me how she mentioned 3 different places she found it in. I've had one more experience early into the relationship which made me think she had intentions to be unfaithful because she thought it was okay to go out alone with a guy friend that I've never met or even known about to drink in a secluded place (thankfully she didn't go).

What I found really weird is that this beanie didn't have any dust on it either, it was perfectly clean and I mentioned this, I figured if it was found on the floor, under the bed or couch then it would be pretty dusty if it was there for a while. I've seen under her couch and under her bed recently but that was just to search for things that one of us loses under the bed or couch like a tv remote or a sock and I've never seen a beanie.

Am I overthinking this? it's something that has been bothering me recently, I try not to think too much of it but I've already talked to a few of my friends and family that are very close to me and they all said the same thing which is that I'm getting cheated on. Any help with this would be greatly appreciated, thanks.

I also forgot to mention that I talked to her about what I think, telling her that it made it's way there SOMEHOW and knowing it's not mine means something was very off about the situation. She started asking if I was suggesting that she's cheating and I originally said no and that I just found it really weird. The next day I texted her about it as I had left to go back home the night before. I told her that I couldn't stop thinking about it because it was just very weird and threw me off, so she started ranting about why I would ever think she would do that. And that's honestly kind of a fair reason because she has put effort into the relationship just as I did, we've had many issues that we fixed but then again I've seen happily married couples having a cheater so maybe even with all that effort that we both put in she is still being unfaithful.