Dentists

Uh so the amt of braincells I hv to be asking this here, but anyways.
I think I got srs cavities. I don't eat that much sugar but I visited dentist with my parent for their appointment, when I was 6? And they made the dentist look at me too and he said I had cavity 4 of my only molars then. Then I thought dentist was joking to scare the kids but now every morning I bleed when I brush. Probably becoz I'm not eating properly because of academics but it's starting to concern me. I don't wanna be toothless tok young in life. What's y'all uptake on this?