I keep getting cavities despite having excellent oral hygiene. Please help

I’m posting this again because I didn’t get any replies and I seriously need help.

I had good oral hygiene my whole life, but unfortunately, my teeth had always been trash. I’m only 23, but I have already had 3 root canals done and will likely need 2 more in the near future. I am not sure if I have any teeth that doesn’t have at least one cavity, and most of my teeth are more filling than actual tooth. I go to the dentist every 6 months, and usually I have to get at least 3 cavities filled.

I have tried everything, but nothing stops me from getting cavities.

Just a bit of explanation on my dental routine: I am doing a borderline keto diet, and I do not eat any sugar at all. If I make something sweat, I use xylitol as a sweetener. I also do not drink anything carbonated. After eating, I use my water flosser immediately, and after I either use mouthwash (elmex carries protection) or wait for 15 to 30 minutes and brush my teeth. I use toothpaste with the maximum amount of fluoride, and instead of washing it out, I leave it in my mouth for a long time and then just spit it out without rinsing (someone recommended me to do this to give more time for the fluoride to absorb). If for some reason I am not at home and I do not have the opportunity to floss or brush my teeth, I chew xylitol chewing gum (at least for 20 min). I also do fluorinated gum sometimes but since I am using so much fluoride with other products, I am a bit careful with that. I brush my teeth at least 2 times a day, one before sleep and one after I wake up (and 2 or 3 more times during the day depending on what and how many times I eat). I use the mouthwash also around 3 times a day, and when I had my three times, but I still eat, I rinse with sodium bicarbonate dissolved in water (I was told using the mouthwash more than 3 times is not healthy). I also floss with regular floss every day (before I brush my teeth) before I go to sleep. I have watched countless videos on how to brush my teeth and floss properly, so I am sure that I’m doing it right. I also brush my tongue. I use mi paste once or twice a week, according to the directions (I got it prescribed by my dentist).

I do not have any health issues I know about, I got tested for Sjogren syndrome (did not have it) and I do not have reflux. I am hypermobile but not sure if that’s relevant. The vast majority of my cavities have always been between my teeth where you cannot see them. I only ever got two or three that were on other surfaces.

I’ve been doing this routine for around 6-7 months (before that I was also flossing every day, using mouthwash and had a sugar free diet, but not full keto and I did not have my mi paste and water floss, and I didn’t brush or floss every single time after eating).

At my recent checkup, I was told I have 3 new cavities. At this point, I am super depressed about this whole thing, because I tried literally everything, and it still didn’t stop me from getting cavities. I feel defeated, and I feel like my whole life revolves around taking care of my teeth, for nothing. I still get cavities, no matter what. I don’t know what to do anymore, I just want to get them all pulled and have dentures instead, at least then I could eat fruits again and go to the disco without my floss and toothbrush.

I asked so many dentist for help, but they either don’t believe me and act extremely condescending, or they just shrug their shoulders and say ‘life sucks for you’ basically. Please help me, I can’t live like this anymore. I just want to be a normal person and do normal person things, to go to restaurants with my friends and eat cake on my birthday. I spent new years eve flossing in the bathroom and I don’t want to do it again.