Why is my dog whining all of the sudden?

Last night while I was getting ready to go out my dog started pacing and whining. I thought maybe she had to go to the bathroom but she peed and then came back in and started whining again. She also hasnt ate since yesterday and thats not like her. I was checking her out and she has a little sore on her foot but shes had that for a month and I completely forgot about it but shes not limping at ALL. she looks nervous when she whines but ive been home with her because I have the weekend off . My dog is a black lab & just turned a year old days ago and shes had her first heat cycle like 2 or three months ago. Also she started chewing again after not doing it FOR 5 months. She ate my flip flops. I am scared something is really wrong with her someone please help me. I plan on taking her to the vet mon but Im hoping I can fix thisproblem before than