First off man, kick back, relax, smoke a j, and think of all the good things you have going on in your life, no matter how small. Be grateful for the person you are, and be happy being the person you are. Get out a pen and pad and write down ALL the shit that makes you happy, and write down your goals. Goals being anything from obtaining your ged, to making somebody laugh, getting a job, or anything you want to accomplish. Be creative about accomplishing your goals, and you don't need to know how you will accomplish them, just know that YOU WILL accomplish them. Don't let petty stuff get you down, just know how you feel is all up to you. This next part is all up to you, but if I were you I would definitely tell your dad he needs help, and be direct with him even though it can be very difficult with him being an your dad. If he is snorting ritalin that shit aint cool, aint no one got time for that. And just like someone else said before, call your moms doctor to let him/her know she is not getting her medication.
PS- try meditation.