There is alot of good advice from alot of well meaning women here. I, however am going to play the devil's advocate.
I do admit the money thing could be a huge issue, but I don't know his reasoning behind it.. maybe that money was needed for gas or something.
But so far as the not showering properly and not brushing his teeth? He sounds like a little kid. If he was the same age as you when you got married, maybe he just never grew up totally. It happens... This could be worked out one way or another.
But.. what if you just want out? What if you already know you want to go sow some wild oats and just need an excuse to leave him? What if the problem isn't him at all. it's you? You have been with him since you were 17. You probably didn't get to date very much before settling on just one guy. What if this is just you getting restless, thinking somewhere deep in your subconcious, that "I can do alot better than this, there is someone a whole lot more exciting and perfect for me" kinda thing?
Marrage isn't easy. It has bumps and upsets and tears. Are you really willing to give up on your marrage just because of something that in the grand scheme of things, is actually fairly petty? Think about that.
It sounds like there is a whole lot more going on with you and your husband, that either you don't want to share (understandable) or don't realize exactly what the problem is.
Also take into account.. if you just want to test the fields out there because you missed out on them when you were younger.. the possibility of finding a GOOD man to take on not only you.. but your three children, and your (now hubby) ex, is very very slim. Chances are alot better that you will end up alone with your kids, or in a relationship that will make you miss his bad breath and smelly butt.
Think long and hard. If you are just annoyed, work it out. If there is something a whole lot deeper.. figure out what it is and try to work it out. Then figure out if your relationship is worth saving. But do not just give up because you are annoyed with his shower habits and a bit of money. Money is the #1 reason couples split up.. but it's not actually money that is the problem.. it's the trust over it that is.
I wish you all the best.