Starter and altenator

Truck would crank and run sometimes and sometimes not. One day I was trying to crank it and battery ran down and I hooked up battery charger that was big and had two wheels to roll on. I put the charger on high/start and continued to try to crank it. L probably did this for to long and some things got to hot but it finally cranked but the starter would not disengage. The only way to disengage the starter would be to turn the switch off and on real quick so the motor would not die. Also the battery light came on so l turned it off and took it to the shop. They said the distributor was bad and put new one on and cranks fine now but the starter still stays engaged until the switch is turned off and on real fast so motor does not die and the alternator light will come on still. L replaced the starter and alternator and still does the same thing. I do not have the money to put it back in the shop. I do not know what could cause this. I really could use some help.