is she cheating?

So a little background... My fiancée and I have been together for 2 years now. She has major trust issues with me even though I've never cheated or anything like that. Recently she's really been getting on me- accusing me of cheating, always checking out my ex's social media, telling me the simplest things I do like going out for coffee by myself, etc. are sketchy. I told her that I can't live my life like this and that it's mentally ripping me apart. Things have been getting better in that aspect but I've been noticing that she's getting a lot of texts from numbers that aren't saved in her phone. So tonight I went through her phone and noticed that she's been deleting her internet history and she has no texts from those unsaved numbers.... I just don't know what to do. Is she cheating? Is that why she's always accusing me? Like what would you think?