What's wrong with my kitten?

My kitten is 12 weeks old. Normally she is a very active kitten. Yesterday, I came from work and she was a little whiny but I didn't think anything about it because she does that when she wants attention. However, she is still whiny today and everytime I touch her stomach she bites at me. My vets office is already closed for the day so I'm turning to the Internet. She had her first set of shots last week so I'm not sure if that has something to do with it or not. She was also wormed, I'm kinda worried because she is also acting like she doesn't want to even stand up. I haven't seen her poop in the litter today but she had a little in there but not as much as usuall. Could this be constipation, or do you think it's something else? Help!!!!! Please.