I need advice on depression or unmotivation?!

Not to be weird but.. ever since im smoked weed, my mood went way down hill. Ive always been depressed and lazy but when i smoked weed it got so much worse. Ive been way more tired and my head feels like im in a constant fog. I dont even look at my homework when my teachers pass it out i shove it in my bag and think yeah right, Im failing everything and when i sometimes get that push that says, im done with this im turning my whoel life around it never lasts ever. I stupidly took my friends adhd pills and felt better, alot better, my head wasnt foggy it was so clear, but it made me very depressed to like im an ugly failure whos life is always going to suck. Please read and try to give some advice and if you would like more information so you could know more you can just ask. But please try to help. Im sick of living like this