Cavities question?!

Cavities question?

Okay so I'm 17 and I went to the dentist for the first time ever a little over 6 months ago, and I had 5 (all small) cavities. Well I got those filled, and I brush my teeth a couple times everyday. I floss as often as possible. Just yesterday I had a 6 month checkup, and I have 2 or 3 more small cavities. Is this normal, or can you tell me what I am doing wrong? Can Gingivitis cause cavities?
FYI- When I brush I use a Sonicare.

1 month ago
I use to eat sweets, and drink sodas. I don't anymore, and havn't in a while.

Most commonly people get cavities in the deep grooves in the biting surfaces of their teeth. The problem here is if your genetics gave u really deep grooves the deeper the harder it is to keep them clean b/c brushing doesn't always get rid of the bacteria that stick down in those grooves so over time you get cavities, OR If u never used to floss those areas were already weakend and that pop u drank or candy u ate sent that weakend area over the edge. But keep up w/ the sonicare they are great and it will help u the most. If you had gone when you were younger they would have placed sealants on those deep grooves to prevent cavities from happening in those grooves.