I drive my car maybe once every two weeks. I got a battery charger and i was wondering should i fully charge the battery before i driver the car every time since it sits there for about 2 weeks at the time?

Does it hurt to battery if i over charge it?

 

Depends on the type of battery charger. "Smart" chargers turn themselves essentially off to avoid overcharging. You're probably fine doing nothing. In the long run, you probably won't get the max life out of your battery, but it's not something worth losing sleep over.
Has a dead battery ever prevented you from starting your car thus far?

 

Mine sits for up to 45 days at a time. No tender or charger and starts every time.

 

well i was wondering if i kept starting the car with low battery could it not kill my alternator?

 

Alternator doesn't have anything to do with starting. Only charges

 

Simply put, overcharging a battery will damage it in relatively short order. Battery Tender style chargers switch to a trickle charge once the battery is topped off to prevent any damage. If i were in your postition, I would spend the $20 or so on a Battery Tender and not think twice about it.