Running for a few days.... sounds like a dead battery due to the charging system. First make sure that you hooked up the alternator correctly in the swap. Then check the alternator fuse. If you're sure that the connections are all good, then your alternator may have crapped on you. Try jumping the car, then measuring the battery voltage. A healthy, alternator driven system should come in around 13.5V or greater. If you're getting around 11.X, then your alternator isn't charging.