I have reappearing swollen bumps that itch, are swollen, filled with liquid and are painful. What are they?

about 2 months ago I woke up with a bite/sore on my calf. It was itchy and looked like a pimple but very swollen, hard and red. I squeezed it and liquid came out and it had a tiny hole that scabbed over and turned slightly purple. A few days later same thing just a few inches away. This has been happening every three to seven days. Some more swollen and harder then others, all scabbed over and slightly purple around the scabbed area. It's really starting to scare me. I replaced my mattress, cleaned under the bed, washed the bedding in hot water and I have a maid that comes twice a week so the house is pretty clean. I have two dogs that both are on frontline. I live in Southern California. Is it a spider bite? Fleas? Staph infection? Allergic reaction? I have no idea and I'm getting really frustrated with this. Some sores are pretty painful and others are not. How should I be treating this? Help!!! Please!!!