Drivers headlight problems. (3rd time!) please help.

[6(sic)6]

at first i had Stock bulbs, then my drivers side burn'd out so i got a pair of h4 upgrades.
installed them then about 5 months after using them. drivers side BURN'd out again.

so i bought some good $38.00 bulbs on ebay.

NOW tonight it burn'd out again.

ive changed the dimmer switch. (even though i know thats not the problem)

but what should i look at and try to fix????????

so that i can QUIT buying bulbs,
this summer im out for college, and i dont need to be dealing with problems with my truck.

ANY advise greatly appreciated.