Pomeranian Puppy - Trouble Walking

My 7 week old pomeranian is having trouble walking. All along he has been a little slower to develop considering that we have had to bottle feed him because the mother died. A few days ago he was walking ok, but still kept his head down. As of yesterday he can't take two steps without collapsing. He usually falls toward the right side, and he kicks to get up and most times he struggles and can't on his own. When I try to prop him up his legs just seem limp. Any advice? I'm taking him to the vet in the morning, but I'm really worried!