Still getting bites on knees after fogging apartment. No bedbugs found. What is it?

For weeks now I have been waking up with small, red, itchy, fluid filled bites on both knees. With three cats, I decided it was best to flea bomb (fog) my apartment to kill any fleas, bugs or spiders, along with flea baths and topical treatment to the cats. I also washed my clothing and sheets in hot water. This didn't solve my problem. I went to the doctor, who couldn't distinguish what kind of bug bites they are. I feel as though I am being eaten alive at night, although this may just be my imagination getting the best of me! I can't seem to figure out what it is or how the hell fix my problem. Please help!!