Seriously depressed...need a dog?

alright heres my story....Im 15 years old..last summer my room burnt down while i was in it and I almost died. Now its halfway through the school year I smoke weed 2-3 times a day im getting terrible grades im criminally truant and have been chronically depressed for months. Basically my life is going down the shitter. Fairily recently i have been spending more time with my girlfriends dog and have found that it really makes me happy to be around. after doing some research i found the type of dog i wanted and preposed it to my parents (I live in a renovated garage room so the dog wouldnt even have to interact with my parents all that much) who had previously said they if they could help i should just ask. Of course after much "deliberation" the answer came out to be a no. The reasons being that there was to much uncertainty in our lives right now. I have this feeling that if i could get a dog I could somehow get the motivation to get my life back on track. Right now my parents are talking about putting me on meds and i have explained to them that it makes more sense to help me with a natural alternative way (getting a dog) than with an artificial potentially damage substance...they just wont listen....i feel like my life is pointless without a dog in it at this point...what do i do?