Alex's medical expenses

Until about a  weeks, Alex was a healthy, average senior looking forward to graduating and going to college. He rather suddenly became exceptionally lethargic. At first we just thought he was having a growth spurt or not getting enough sleep. But when he missed 10 of 15 days of school (so far) we knew something was wrong. Alex doesn't like to miss school. We've been to three different doctors so far and had numerous tests done and still haven't been able to discover what's wrong. Meanwhile, I've had to miss a lot of work to take him to the tests and the bills for those tests are starting to roll in. We recently switched to a new doctor when our regular one essentially gave up looking and we are hopeful that she will get to the root of the problem. 
Our family lives paycheck to paycheck so there isn't room for missing lots of work and having lots of extra bills. I know doctors offices and hospitals will work with us on the bills as long as we pay something but it doesn't work that way with car loans, mortgages and utility bills. 

We covet your prayers most of all but anything you can give will help.