My partner 34M spent a whole day with his ex girlfriend 38/F of 10 years with our two children 3 and 1. Hid it from me by deleting conversations and photos.

I just recently found out that my partner whom I live with and have two children with. Hung out with his ex of ten years at his mom's house all day with our kids.

How I found out, my daughter had his phone and she was taking photos of me (she is 3) I didn't like the photos and went to go into his phone to delete them. come to find out his phone has a different password. hes currently in the shower so I asked him, " why is your password dchanged? can you pleas give me the password so I can delete these photos our daughter took of me?" gives me the password then I asked him why it was changed? he made up some lame excuse that he had some basic password that people seem to have..

I go into the photos delete the photos then go into deleted photos and there it is a deleted photo of his ex sitting there with our little boy who is one years old, I looked at the date and it was Feb 22nd. I just found out yesterday.

I brought it up he lied, also was trying to get me to bring him his phone this whole time im on it and I said hold on I want to delete these photos.

his story.. his mom had plans to see her and he went to go drop the kids off at her house and she was there randomly.. so he was happy to see her and so they hung out for the day with the kids.

seems so completely harmless yet,.. he deleted the photos, deleted the text message conversations between them, hid it from me, both him and his mom, I feel betrayed. his mom I Brough it up to her she calls me insecure. can't stand her. so here I am being lied to, not being consulted by my supposed support team. not sure how I should go about this?