I need advice :/

My boyfriend keeps flirting with other girls.
I still like him a lot though so I want to avoid breaking up. (I fake broke up with him once to see his reaction, and I know for a fact he really loves me. He went into spiraling depression.)
But this is bugging me a lot. Ripping my heart in half.
Part of me wants to give his face a high-5, but the other half won't let me. Please give me some advice!