You're situation is a bit complicated because you are missing chemistry and organic chemistry, which is required for all US dental schools. Maybe enroll part time in a local community college to get the credit and, more importantly, the knowledge of basic chemical principles which will prepare you well for the DAT. You might want to consider brushing up on your Biology and Physics, too, as I believe they are also on the DAT.
Another good option is to try to get into some kind of Post-Baccalaureate Pre-Med/Dental program that accepts people who are looking for a career change who haven't completed all the dental school prerequisites. These programs can be very competitive, but they are looking for people in your situation who want a career change. The only downside to applying to one of these programs is you need to have taken the GRE/MCAT/DAT within the last three years and you may need letters of recomendation. It may be worthwhile to look into.
Also, you could very easily go to a local technical school and become a dental assistant or a dental hygienist. If you can't end up getting into dental school, but you really want to be a part of a dental practice, this is a good option. The people I know who are dental assistants/hygentists really like their jobs and you could even do it part time in addition to the job you have now.
The other thing you have to consider is factors you can't really control. Is there a dental school near where you live? Are married? Do you have children? Do you have the money to finance four or more years of a very, very expensive education? There is a lot to think about.
If you are really serious about becoming a dentist and there is nothing else you would rather do with your life then go for it! You only live once, so you might as well try. You don't want to end up on you're death bed and wondering about what could have been. If it works out, then that's great great! If not, then at least you will know it wasn't really for you and you have a lot of experience working in another career, so you will probably be able to get a good job in the field you are in now.
I would also say don't quit you're job during the application process. You will need to continue to support your current lifestyle and the applications to dental schools are way overpriced.
Good luck!
