bumps on gums

I have been to the dentist twice recently. First I had cold/hot sensitivity which was new. He checked my teeth and couldn't see a problem. Since I'd had a cleaning within the month he thought it was from that and told me to use synsodine, which I did. A week later I noticed a red bump on my gum in the same area. I went back thinking it was an abcess (abscess). He checked me again and did an xray of the area. He didn't find anything wrong with those teeth. He prescribed an antibiotic which I am taking now for 4 days. Now I notice smaller whitish bu,ps around it. I brush daily, floss fairly regularly and have regular dental visits. I don't smoke or drink. Sometimes the bump hurts but usually not.
What do you think is going on?