I think my cat is sick from vaccines from the vet says no!?

I am very concerned about my 3 year old female cat. I took her to the vet about 2 or 3 weeks ago for some vaccines (she had never had any before) and she got I believe 3 of them (I know one was for rabies, and I can't remember the other 2 but one was I think for lukemia?) I went out of town two days after she got the shots and came back a week ago (house sitter didn't mention any trouble with her) and noticed that she was not acting herself, she's usually very friendly and runs up to people but she wouldn't budge from her bed. I thought at first that maybe she was just mad at me for being gone but I realized that she felt very warm and her eyes looked tired. She was still eating, drinking, and going to the bathroom but not as much. She also seems to be twitchy which makes her hair stand on end a little. I did research online and it seemed that she was having a reaction to the vaccines she had gotten. I just took her to the vet and she's gone form 11 pounds to 9 pounds in just a few weeks. The vet said that it couldn't be from the vaccines and they just took some blood and said they would call me tomorrow. I still feel like it could be from the vaccines since I read so many online accounts of cats acting just like her after vaccines. I want another opinion but can't really afford to take her to another vet. She is acting like she feels a little better, maybe, but I'm so nervous that the vet is wrong and that she will just wither away. What should I do?