Is it normal i can't afford the dentist and have five decaying teeth?

I've been trying to save up but I'm really in debt as it is. I still have to pay my cell phone bill from a month ago and I haven't hung out with a friend in a month because I'm saving up to pay that phone bill.

I brush my teeth but I guess I mostly focused on the front ones and the top. But for the past year, I've had issues where my bottom teeth had minor cavities..now they're huge and the last time I was at the dentist and had one of them removed, it was $400. I simply can't afford any more right now and will have to save up for another 6+ months to get one more removed. It's sad because there was one that was still small but now it broke yesterday as well so I guess I have to have that removed as well. :( It's like there's no end to this and they keep getting bigger and bigger even though I now mouth wash three times a day, don't eat much solids, only drink water and brush them lightly (can't brush hard, it hurts/they're broken up already)

I don't want to have to get dentures or more extracted but I notice with every 2 months or so, another is more broken than it was. But they said I'd need 5 root canals and root canals are $1,300 a piece because they also include caps. I can't afford even one root canal. I am so upset with myself for not having brushed harder but I never understand why they get worse if I barely eat/leave them alone/mouth wash.

I told my dentist I can't afford much and they are aware but the last time they still tried to make me pay $500 up front and I said I didn't have that so they said they'd be lenient and they gave me a month to pay that off but that was all I had and they said they'd never do that again. :(

IIN?