How to recheck collision?

I can't find anyway to check if there is currently a collision between two objects. I have a ball that is controlled by the user. OnCollisionEnter with a platform makes some variables true, necessary for my dynamic jumping system. OnCollisionExit also causes some variables to change. However, the platforms are moving, and will even move through each other. There is a bug which disallows the player to jump even if he is currently in contact with a platform because OnCollisionExit was called when another platform passed underneath it. The only solution I can think of is to check for a collision manually, which doesn't seem to be possible.