What would you think his reasoning is...

A few weeks ago I had this feeling in my gut that my husband was either hiding something from me or cheating on me. So I went threw his phone while he was asleep, I know I shouldn't have but I wasn't expecting to find anything on it since he tells me everything. Well I went into his pictures and found a recent picture of his ex gf she's also his 1st baby mom.

I looked at the details to find out what day it was and it was the day after I had just delivered our son. I asked him about it and he says "he doesn't know why he did it." What would you ladies think why he would really take a screenshot of his ex's picture that she took of herself on Snapchat? I honestly don't believe him and not sure what I should do about this.