Van air conditioner not blowing cold air?

I have a 1998 Oldsmobile Silhouette. I just bought it last December. When we bought it the air conditioner was blowing cold but being december it would be cold outside as well. Then spring got here and now it's 86 degrees outside and the air isn't blowing cold anymore at all. I tried recharging it followed the directions on the can and did just as it directed and the air is still very warm and humid. A little insight, I had to change the serpentine belt when I first got it because the belt was very warn. Well then about 2 months later the belt broke and I found out I had been given the wrong belt at the part store and had to replace it again. So I did. Well now it is squealing again. This is about 3 months since the last time I changed it. It just started. I am wondering if these two problems could be related since the compressor is also on the serpentine belt. If you can give me any ideas on the solution to one or both problems it would be greatly appreciated. Aside from this issue it's a great van.