Recieved a 1099misc form for tribal per capita, i already pay federal tax eaach month when i receive my per capita. how come when I enter in turbo tax i get taxed more?

Your per capita income from your 1099-MISC gets added to the rest of your income, and the tax gets figured on all your income, not just the tribal per capita income. So the amount withheld might not be enough to cover the tax on your total taxable income.