2006 Ford 500 AC/ Heat air pressure pulsing

The past month my car starts about a half second late. This happens once in a while. Today, on my way to work, it was cold so I tried to turn on the heat. The heat was set to 78, and only a hissing sound came out, no air pressure. I tried to mess with the controls of the temperature, pressure and the button to use the air within the car. Nothing seemed to work, however, when I started to get on high way, there was a be burst of air pushed through. I turned the pressure down to low, once I did this it completely turned off again. I left it as that. Its an hour drive to work, so about half way there it came back on again, and I kept it at the low setting, but my check engine light came on. Once I got to the town and off the high way, it started pulsing on and off. I noticed this happened more often just after I press the gas after being on the break for a red light. Could it be my alternator? Or air compressor or something else all together? I am good with my hands to try and fix by myself, and can't afford hundreds of dollars for someone else to do it.