If I had air in my brake system could it effect my clutch pedal if they share the same reservoir?
The hydraulic systems for your brakes and clutch are totally separate. A bad throw-out bearing would not cause a clutch pedal to be hard to push, it would likely make noise however. If there's no excessive sound coming from that area when you depress the clutch in my mind that would eliminate the bearing. Your issue may come from either a binding clutch pedal pivot or more likely, a faulty master or slave cylinder. You didn't tell us the mileage on the vehicle or whether you're having any shifting issues along with the stiff clutch which could help diagnose the problem.
Start by checking the pedal pivot, if its free, I'd then replace the clutch master cylinder as its easier and cheaper than the slave. Its unlikely, but there could be binding on the push rod that goes from the pedal into the master cylinder but it should be obvious.