I need help

Hi, I am new here. This is my first posting. We recently took in 3 foster children. We have no children of our own and when we started with the foster care system, we said we wanted one or two. We are wanting to foster to adopt. Our worker asked us if we would be willing to take 3. We talked it over and decided we could handle it. We were told the children had no exceptionalities. We thought we could handle 3 normal kids at once. Well, they are here, and I am so SO overwhelmed. I just want to lay in bed and cry every night. The oldest girl had ODD and is on 3 medications (we didn't know this till after we took her in). The youngest are twins-a boy and girl. The girl has major issues with her temper and has thrown her dinner when she doesn't get her way, pushed the dinner table across the room and has had days where she screams from the moment she comes into the house. They've only been here 3 weeks. I've made positive behavior charts for them, schedule charts, etc. I just feel so overwhelmed. I feel like I've made a mistake and I wish we had taken fewer children. This is our first experience, and these children are supposed to be foster to adopt. I don't know if I can do it. I feel so stressed, I don't find myself bonding to them. I've called the older girl's counselor and she has never returned my call. The boy tries to hump his sisters when they are alone in a room even for a moment. I feel like I have no support from DHR and I feel like I was misled on their issues. I am totally unprepared for this.