A quart is 2 pints. A pint is sixteen fluid ounces of water and weighs about 16 ounces (avoirdupois weight.) A gallon is 4 quarts (8 pints) and thus weighs about 8 pounds. Five gallons would be about 40 pounds.
In some cases, if your mother is on Medicaid, she can designate you as her personal home care aide and you can get paid a small amount through Medicaid. If your mother has her own resources, you can draw up a contract agreeing to work as her home health aide and she can pay you a salary that you both agree upon.
So if your parents refuse to pay, you will have to make up the difference. The school and the government will not help. Talk to your parents and lay out all of your finances in front of them. Show them how much money you have and can earn, demonstrating that you're doing what you can to cover the costs.