Electrical and engine problems

for 2 weeks my battery would go down to 8 amps when i was at a light then go back up to normal when i took off. Had the alternator and battery checked they were fine. Then today i go to work and when i pulled out of my driveway and put it in drive and stepped on the gas my whole car started to shake violently. Same in reverse. All my gauges were fine but i couldnt get any speed and the harder i pushed on the gas the worse my car would stutter and shake. I got a 99 camaro v6 with 41000 miles and never had a problem with it till now. Figures my warranty just went out. how bad is this and how much to fix. Any help would be great. Thanks

have the car scanned for codes, no way to tell you about how bad it is or how much to fix if we dont know whats wrong with it.