4 yr old reverting back

I have always had a problem with toilet training my 4 year old son. I had him fully toilet trained in april this year taking himself off to the loo for pee's and poo's he was so proud of himself and i praised him for his efforts i was so proud he finally got it. Soon after my 2 year old son started to get in on the action and also had no accidents for around i month i was over the moon. But in the last few weeks it has all gone backwards thinking i was free of nappies and pull ups, i went back to what worked and that was a reward of a choc drop when they used the loo. It has not worked now my 4 yr old takes his pants off pooing on the floor then he used the curtain to wipe his bum. He hoped on my bed and wee'd on that. I don't know what's wrong and how to stop it. Even before he was trained he never did things like this. I don't know what to do with them. Help

Have there been any changes to the family? Babies? Work? Relationships?

The routine has not changed but being a single mum i do shared care with the father. For the few months that the boy's were trained the father would not believe me. He said they still would not use the loo for him. I don't know how he delt with the situation i'm hoping it was not with smacking but he does not communicate with me very well. When we were together and i was trying with the eldest boy he would swear at him and put him outside. Broke my heart that was the day i left. He now lives with his parents and thats where his visitation happens so i have my fingers cross his parents would not let things like that happen. I feel so out of control when it comes to my kids.