Question about change in behavior?

I have a 2 year old cat that has been part of the family since 2/12/11. I have never had a cat before so I am trying to not over analyze his behavior. Abraham seems very healthy and VERY energetic. He is completely an indoor cat. He eats a combination of Blue Buffalo wet and dry food. He eats the recommended portion split up between a morning and a night feeding. He usually runs right to his dish and devours its contents. He drinks all of the time both from his and the dog's dish. Last night he seemed a bit different from usual - he kind of just laid around all night. This morning I put his food down which he was begging for and he went right to it and did not eat. I left him alone for a while and figured he would it it if left alone. I came back a while later and it was still there so I gave him a different can of the wet food that he loves the flavor of and he ate that but kind of slowly. When he was done with that I tried to give him dry food but he walked away. I also noticed that when I first put his food down this AM that he started kneading the floor by his dish. My partner said it looked like he was ready to use the bathroom! I called his name and redirected him at which point he did go to the litterbox and he urinated. All bathroom habits seem in order. I checked his teeth to see if they were ok and that checked out. He does not have an abscess in or around his mouth. He was treated two weeks ago for a torn nail which is completely healed. Am I paranoid? I tend to think the worst. Any guidance would be so very appreciated!!! PS I am not sure if he ate some left over dog food that my dog may have left.

back to me. I usually take up any unused dog food immediately, but I must have forgotten. I can't get into a vet until Monday I was kind of wondering if cats get stomach aches?

Abraham ate all of his food tonight and is running around the house!!! I think he probably was full because he ate some of the dog food last night!