Dextrose is just corn sugar.
Also, you should really consider buying your supps online. A tub of 5lb ON Whey is like $25 or so from
http://www.bulknutrition.com
They also sell dextrose...
Other then that, what is your total caloric intake? And how many grams of protien/fat/carbs are you getting a day? It doesn't seem like you're eating enough to grow...