I have a LOT of the same issues as you, I'm 15.
I would say to go to your doctor and just have them check your iron levels to see if you're anemic, which it sounds like you are.
They can have you get some Slow FE Iron pills to start to regain the iron in your blood.
That's most likely the result of your fainting and weak strength.
I experience a lot of the same problems.
I go through a Super Plus tampon and pad in 2 hours.
And I'm on BC Pills too! Take them every night. I dont know exactly what's wrong.

i am not a fan of the depo shot. it angers me when doctors put women on the depo when they are having a bleeding problem, when the depo's side effect is that you can bleed for upto one year.

i had a bleeding problem called dysfunctional uterine bleeding and they put me on the depo and i bleed fora long time. i got that stuff out my system and i started birth control pills and i stop bleeding in three days. i struggle with heavy bleeding for almost a year and the doctor was playing trial and error on me. finding out what works and what doesnt.

the depo can cause you a lot of grief, fainting, lightheaded, etc- you can stay on it and ask your doctor for another progesterone shot because your period is still on, and this might stop it.
you can wait until it gets out your system and get on the pill.

the depo only have on hormone called progesterone. most birth control pills are combination hormones called progesterone and estrogen.
i m going to email you something to educate you on your problem.