Hi, my chihuahua has not gone poop in a long while. Is there something else wrong with her?

She just had femoral head surgery a few days ago for her joint disorder (perthes disease) & just found out she has a urinary tract infection also. She is turning 1 in a few days, so she is still a puppy. She usually goes poop before she goes to sleep @ night and when she wakes in the morning. Now she has not gone at all since yesterday morning. There was a little pebble of poop that was next to her as she was taking a nap during the day, but that was it for the entire day. Do you think its because of the antibiotics & pain pills that she is taking or is there something else wrong with her? Thanks for your help.