Something in My Apartment Smells. I just Can't figure out what it Is?

I’ve rearranged furniture and vacuumed everywhere. I checked the crawl-space in my closet. I’ve mopped the kitchen floor and cleaned my bathroom. I’ve sanitized the refrigerator. Still, there is nothing I can do about it; the smell just lingers and honestly seems to be getting worse. Lysol spray helps, but only temporarily. Candles just cover the odor and almost seem to mingle with it. I’m getting desperate and I don’t even want to have anyone over – I’m embarrassed. Has this ever happened to anyone? What do I do?