ok.. so yesterday we went to a B B Q and accidentaly forgot the dogs food at home soo everyone was feeding them rib bones and meat and stuff.. and they were fine.. well we took time home and everything was fine and when i woke up this morning she herd me and started crying when i touched her she yelped.. so my boy friend took her out thinking maybe she just really needs to use the potty.. and she walked down the stairs fine but walked really slow outside and wouldnt leave his side,, and thats not like her at all.. then whe she came back up the stairs she had a hard time..and walked kinda funny.. i was petting her and noticed that when you pet her on the top of her hind legs she cries.. also its like she is in pain but trying not to be.. she jumped on my bed stood there for a few seconds and jumped down.. when she jumped up she cried but not when she jumped down.. any ideas what might be wrong with her?

I am taking her to the vet today.. just wanted to know what to expect or if maybe the vet couldnt do anything for her..