Sadly it sounds like a leak. A/C is usually expensive and not easy to fix by yourself unless you know what to do and have the proper cert. to repair automotive a/c systems. I paid over 400 dollars last summer to fix my girlfriends 93 accord and that was just parts, I did all the labor since I'm a technician. Let's see those parts were like 300 for an evaporator/expansion valve, and about 100 for R12. That was for a leaking evaporator. Just one part and it adds up. You need someone to tell you what's wrong.