Concorde electrical? Desperate for help!

I own a 98 crysler concorde with 75,000 miles and 3.2 engine. The car runs great--when its working. After being jumped the car will run for about 2-3 minutes then cut back off again. Since I have had the car, it has had to be jumped every now and then. Eventually it got to a point where it seemed as if the alternator was not charging the battery long enough to stay running. I replaced the battery and it worked temporarily, then jumped again. I replaced the wireing from the battery to the alternator and it worked great AND the battery finally tested as a 'good battery'--then had to be jumped again. I took the alternator out of the car and took it to 3 different shops 2 of 3 saying the alternator is working fine. One mechanic told me it seems like an electrical problem. I am so confused and will take any advice I can get. The car is obviously made as backwards as they get. I am a single mother and I go to school. School starts in 2 weeks, and without this problem fixed, I'm at a loss and cannot attend school. I would love to give the small donation this webpage is asking for, but I'm so over broke I don't know what to do. Please help me. I am desperate for answers.