What the fuck

So me and my sons father got back together recently and he is always accusing me of cheating and i havent so i decide to go to his messaging app on his phone and restore all of his deleted text messages well i seen a message that said "definitely milked my ass lol" and "need it soon" so i said who the fuck is this and he gave me 3 different excuses so i said let me call it he said no I said yes let me call it and he hurried up and deleted it and said yeah my cousin used my phone because his phone was off that day so i went to his cousins messages and on that date they had texted so i know that was a lie... I just dont know what to do I dont believe him at all about it and i have that gut feeling that he did something and im never wrong when i get that feeling... ): and hes changed his number and has changed his pin on his phone like 4 different times. He "deactivated facebook" and doesnt get on messenger but reinstalls it everytime hes not around me. What would you guys do?