I dyed my hair about two weeks ago back brown because all my ginger was showing through, and now tried to get it to go back blonde and it has just gone back a red ish colour with light roots. Can I dye my hair back brown without it falling out?

The problem is, with so many different kinds of dye in your hair, there's a good chance of them reacting to each other and causing your hair to turn God only knows what color! I suggest leaving it alone. Possibly waiting for it to grow out.