Having the divorce conversation

So I have been away from my husband for a little over six months due to COVID-19 and him being overseas. He cheated on me last year, and we been trying to work on things. Being away has made it easier for me to see I am not happy and cannot move past the infidelity. He’s coming back in about 3 weeks and I don’t want to blindside him. How do I bring up at least separating?

Side note: We have a 3 year old daughter. When he cheated the woman ended up pregnant. She chose to get an abortion.