I have access to his iG acc and he doesn’t know

My boyfriend logged into his iG on my phone and didn’t log out . And he hasn’t messaged anyone he’s not suppose to but I noticed he has been searching for girls and stalking their profiles or something ... some are regular girls that went to our high school but post some pretty revealing stuff ... and the others are random accounts of women with sexualized content ...

How would you feel about this? I’m so confused as to what I should do .