Do I need to test my dog for worms before treating her for them?

She shows all of the symptoms for worms (except for the pot-belly which applies to puppies). She started with the " scooting" and within a couple of weeks she started throwing up and having diarrhea (which lasted 2-3 days). She has lost at least 5 lbs over the last week and is weak. She has finally started taking small amounts of food a couple of days ago & I plan to go to the pawn shop tomorrow so that I can take her to the vet, but don't know if I can come up with enough money. Before you get nasty with me, I am disabled with no job and this is my child whom I take better care of than myself!