Periodontitis around 3mm-5mm?

Hi all

I've been suffering from a lot of mental health battles for the past 2-3 years (specifically GAD, depression, and the sudden death of my dad), which had resulted in me having less than stellar oral hygiene. I use to go to the dentist 2x a year when my dad was alive but I hadn't gone in 2-3 years due to my GAD and my dentist being slightly judgmental and scary.

A week ago, after an anxiety attack, I decided to get serious about my oral health and went to see the dentist today after having some painful gums (I went to see a new dentist). The dentists and dentist hygienist did some charting and the dentist hygienist was saying that most of my teeth were around 3mm-5mm (with one tooth being 3-6mm). They told me I had Periodontitis but it was the early stages and if I continued to brush my teeth and floss that it would be okay and to come back 2x a year because I'm still "young" (The dentist also said I had some sort of viral infection going on causing some canker sores near my gum line and I was brushing my teeth too aggressively which caused it to be inflamed and when he looked at the x-ray scans he said my teeth looked healthy and I just had to fix a minor filling leakage which I did).

I get back and I start looking this up and IT FREAKED ME THE F..K OUT. Due to my anxiety, I can't help but think that the dentist didn't tell me the whole truth because this one tooth (most likely the one with 3mm-6mm) has become sensitive after the cleaning. But logically, I keep trying to tell myself that if there was an issue, the dentist would have told me about it, but I'm just curious as to what it means when most of my molars are around the 3mm-5mm stage? I know that regardless I need to really maintaining and improve my oral hygiene so it doesn't get worst, but am I really in the "Okay" zone if I just continue to brush, floss, mouthwash and visit the dentist 2x a year because I'm "young" (just turned 25) or am I already at the stage where I have inevitably ruined my teeth and suffered from bone loss?

(Sorry if I seem stupid, working on my GAD but the obsessive thoughts are still something I'm struggling with)

TLDR: Does having 3mm-5mm (with one tooth around 3mm-6mm) mean I can stop my gums from receding if I maintain a proper hygiene practice or am I in the "too late, go see a periodontist" phase?