My Pug Is Sick Again With Crystals In Her Urinary Track?

I've had my (almost two year old female/spayed) pug now for since last August. She was fine until I went away for a week vacation (leaving her in her own home with my 20 year old son who loves her, plays with her, walks her, etc.....) and came back to find that a day or two later; she was not peeing; except maybe once a day. After day two I called the doctor and got her in on day 3. She started developing crystals in her urine track; not a good thing, but after pee tests and anti-biotics; she cleared up fine and started peeing again several times per day. Then about a month later, same thing, went to vet, crystals present, cleared up.............by the way, I also changed her diet as suggested and everything else they suggested to get her to pass he crystals........and she was o.k....now, same thing...........past several days she will pee o.k. then not pee most or all of the day...........there has got to be something that I can do long term to help her with this problem. I've spent around $650 in vet visits, tests, meds, etc........in the past few months..........now don't get me wrong.....she is worth every penny and more...........she is wonderful! I asked the vet if vet insurance would be a good idea.......I had a long talk with the assistant and she said "no" in the long run it would cost more.......o.k............well, between everything needed to keep a pug happy and healthy (wipes for wrinkles, ear cleaner/swabs, special diet, groomer (I don't cut her nails, they are dark and I am afraid to make a mistake).........special allergy shampoo, etc............she costs me more than the rest of my family............lol...........once again, not complaining, I did my homework........but.............she is sick way too often..............Any help would be appreciated.......If I lost her, I'd be devestated!