Can I get my Foster child back even though I turn him ?

I'm a foster mom and was taking are of 3 children and I also have 2 children of my own which was 5 kids in total in my home and I'm also 8 months pregnant. I felt so overwhelmed that I wanted to turn in 2 Foster children and just stay with one but unfortunately my caseworker ended up taking all 3 of them. Now that they left my family are so devastated especially my son that has been crying non stop ever since they left. The foster children were living with me for a year and got taking away a day ago.My question is, even though I turned them in can I still try to talk to my caseworker to see if I can get them back? Or is it too late? And by the way they are up for adoption soon, so I also wanted to know if I can adopt them if I do get them back. I know I said it was very overwhelming for me but now im willing to deal with it and I also have a lot of support with my family..I just wanted to know if anyone can give me any information before I call my caseworker.