I'm just coming back to say that I am so glad I rode it out!
My hair is great now! I even know what I was doing wrong, I was washing it with bicarb but I wasn't conditioning it at all, as soon as I used apple cider vinegar, my hair is completely different! I've had no dandruff at all and it's no where near as frizzy as it was.
I don't think I will ever use shop bought shampoo and conditioner again.
Oh, and I ended up cutting my hair, I chopped about 15 cms off the ends, as I couldn't stand the feeling of dry ends and oily roots. I'm regretting this a bit now, as it wasn't necessary, I just needed to use the apple cider vinegar. But at the time, I considered shaving it off! That's how much I hated it at the time.
I'm now looking into making my own soap so that I can eliminate all the chemicals that touch my body.