A few days back, my gum around one molar started swelling. I saw a dentist, he told me it was gingivitis - gum infection- and he did scaling on all teeth. He also prescribed Chlorhexidine solution as an anti-septic mouth wash. After 3 days, the swelling nearly went away (90%).

When I went to visit him again on the 4th day, he told me that all of the infection hadn't gone away and performed deeper scaling on just the affected tooth/gum area. This time, its been about 3 days now, but the swelling seems to be coming back. Its like about 30% of the initial swelling back again. The area is not firm yet, and is a bit sensitive. The gum area there doesn't bleed when brushing though.

Can someone explain whats happening here?
Appreciate your help.