Need help with car a/c problem?

Hi. I have a 2000 Chevy Cavalier and my a/c is psychotic. It goes in and out about every 2 days. I bought a can of car a/c and took it to pep boys to help me put it in. they concluded that my low pressure valve has to much pressure. they suggested that I have it recharged for 169. please help...its getting hot in georgia and i kinda need my a/c.