I asked in game about how to call a medic and someone said that you press Q. But I couldn't get it to work, so maybe this person was pulling my chain.
How do you call for a medic?
On PS3, you have to target a medic of your team (i.e. look at him with your crosshairs) and press Select.
You're on PC and Q is the right key, so I'm guessing the problem is you didn't target a friendly medic with your crosshair first. They have to be close enough. If it works, you'll hear your guy screaming out for help.