Air conditioning blows hot

Recently, my air conditioning started to blow warm air and would occasionally blow cold again. For the past week it has completely stopped blowing cold. I purchased a can of refrigerant that came with a gauge. When I first put the the gauge on the low side, the pressure was in the red. I proceeded to let out the refrigerant that was in the lines (which only air seemed to come out). Once I got the the gauge to read that the pressure was low, I started to fill the system up with the refrigerant. I’m just a couple minutes the pressure shot up into the red before I barely had a chance to put the refrigerant in. Does this mean there’s a blockage in the line? If so, how do I clear out the lines?