I did some part time work starting when my baby was 2 months old, but I always brought him with me. So he was with a babysitter, literally in the room next to me, and I would pop in and visit every hour or so. I would "leave" him with his dad for half an hour or an hour while I went running. Any longer than that felt unbearably long.
When he was about 8 months, I got a gig that would keep me away from him for two whole hours and I'd have to leave him in the house with a babysitter. That seemed almost impossible to do, and I cried in the car the whole way to the gig.
When he was 9 months, I went back to work part time for real and left him at home for 3.5 hour stretches. It was also really difficult, but we managed. Now he is 18 months, and I leave him routinely for 4 hour stretches to work, and sometimes for about 6 hours.
Sometimes I talk to other parents who've left their children overnight, or at bedtime. That seems unimaginable to me... but maybe I'll get there one day.
It's a process, Mama! You guys are going to do fine.
What you are feeling is pretty normal.