1997 Ford F-150 Strange clicking

I just bought this truck two weeks ago and it had no extra little noises for the first two weeks. But the other day it started squeaking a little. I can deal with a little squeak thats fine. But today when driving I hear a very audible clicking or clacking noise. Its only when im on the throttle in drive. In neutral reving the motor there is no noise. So I was hoping someone could point me in a general direction of how to fix this problem, because frankly its a little embarassing. Thanks for all help givin. Justin