Nagging feeling husbands cheating.

I just had a baby 11 days ago. Before I went into labor I saw what looked like my husband ex wife name on his phone. I didnt say anything because I didnt feel like starting conflict and honestly ive forgotten about it with a newborn and all. But its popped into my head a few times and when it does I just get this horrible feeling hes talking to her or seeing someone else. What should I do? Hes never given me a reason not to trust him and I've never been suspicious of him. But lately the feeling creeps up on me and I dont know why. Hes also doing this this with his phone now where hes flipping it upside down so the screens facing down when hes not using it. Hes never done that either.maybe it's just hormones? I love the man more than anything and it would crush me. I just dont know where these feeling are coming from