having on and of irritations in my vagina

I have been having on and of irritations in my vagina, i was first treated for scabies, which didnt work, then treated for thrush, i have even used fungi cream. None of which worked. Sometimes the irritation will go and then sometimes it will arise again. I decided to have a look at it and i realised there is a slight small slit in my inner lips, it is also very red in my vagina, im very woried as to what it could be when i saw my gp she could not see the slit. I beleive it might be the slit causing my irritation, but i have no way of knowing how to heal it, it has been over two weeks now. please help me...