Single mom, afraid of losing my child

Me and my ex split up 12 days ago, the day he left me and our son was the same day he got a new girlfriend. I was the primary care giver, went back to work when my son was 8 weeks old because my ex would get mad that inwasnt doing anything. I started working nights 11-7. I would take care of my child go to work come home and take care of him again. My son is now 6 months old and thats the way things were. Since we split i took my son to his dad for a visit and after an hour he didnt want to be around his kid anymore. He drinks everynight and always has his new girlfriend over. I let my ex take my son 2 days ago for the day. He had him for 3 hours. I picked up my son and was informed he had a haircut which was his first and i dont even get a lock if his hair. Now my ex is trying for full custody. Im scared im going to loose my child