Please, tell me if this is cheating or not?

My partner was in this smule app, at first i told him i dont mind him using that app, but just dont talk to any girls. Cause he doesnt let me talking to guys. He told me he wont and hes not talking to any girls.

Anyways, i found out he was lying to me, he was talking to girls. But ehh, i just let it go. I then had a feeling somethings off, so i went to his acct, and i saw that he was flirting with one of the girls.

Flirting IS cheating to me.

He wrote to her that she is amazing with this kissing emoji 😚 just doesnt have the heart on it. Anyways, i left him for it, he told me that it isnt cheating. He was playing dumb that its not a kissing emoji, its a whistle emoji. -_-

He used that emoji to me too when he does muahh.

He said this isnt cheating and that im stupid for leaving him for it. He said someday i will look back at it and regret my decision.

So i was just wondering, is this stupid for me to divorce him? And is this cheating? Or hes right that i overreacted and it isnt cheating?

Im currently pregnant too, and we have 2 kids under age 3... i feel betrayed. He did this to his ex wife too when she was pregnant. Now hes doing it to me. Hes 30yrs old, im 23. Hes trying to cheat with a 22 yr old.