Juan,

Do you have an explicit agreement of exclusivity?  Have you talked about respecting the relationship by not flirting with others either online or in person?

It may be worth a sit down conversation on what you like to see in a committed relationship, e.g. no porn or keeping in touch with ex girlfriends or flirting with other girls or being on dating websites/apps…  whatever it is.

This way he would know what your want from him and from the relationship and visa versa.

Mark