How do you let a family go from daycare?

I have been caring for an infant for a little over 6 months. He is an only child and I had a lot of work ahead of me to get him out of the habit of needing to be held constantly. I had noticed an improvement and he was really starting to find his own way, playing, sleeping without being held, scooting around, it was great. Mom has recently cut down to part time and all of the work I have done is gone, he is right back to screaming if you put him down. It's an all day thing. I have other children that need my attention and I feel like I can no longer provide for him, oh, I am also expecting myself. I have tried to talk to his mom, but she laughs it off or blames teething. I truly love this little boy, but feel I am not able to meet his needs and the other childrens any longer. Soooo, how do I tell mom?