I have a 2003 Hummer H2 with approximately 39,000 miles. This morning I went out and the rear end of my Hummer was sitting very low. I know that there is a button labeled " height control" in the Hummer and that it has rear air suspension. No one touched the button and I don't know what possessed the Hummer to all of a sudden drop down when it was at a normal height last night. Nothing has been added to the rear cargo area. What do you think happened? Is it still safe to drive? How do I fix this problem and bring the rear end of the vehicle back up to match the height up front?