Frustration and spending

Gah, I'm so frustrated! So, Jason and I bought a car at the beginning of this month. We had to put down a big down payment because we didn't want the monthly payments to be over a certain amount. Then, yesterday and today, we start getting bills in the mail for medical and dental appointments that I went to at the end of May. Apparently insurance is not going to cover nearly as much as we thought it would and we not have to pay several hundred dollars to these different places for services that we thought were routine. For example, the insurance is not covering any part of my annual OB appointment. Those are practically required and are good for preventing any kind of illness, and yet they don't cover ANY of it!! And my dentist... I just had a bunch of cavities filled but the insurance is not covering as much of that as we thought they would because "the cavities are on the back teeth" and they don't cover the back teeth the same as the front teeth. This is ridiculous!! Thankfully I got my 5-in-1 check yesterday so we won't be terribly insufficiently funded, but I just wonder why we have insurance if they don't cover these simple, routine things. What is going to happen when I am pregnant? Are they going to cover any of it? It makes me want to scream.