I never knew that is not good to do istinja with your right hand, I have been trying note to use my left hand for Istinja, but I can't seem to reach the back area and clean myself properly with my left hand, so I then finish off with my right hand, is that ok, since I know I wasn't able to clean properly with my left?? I'm so confused.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

Washing one's private parts with the right hand after relieving oneself is forbidden. The Prophet said: "One should not touch his penis with his right hand while urinating, and should not wash his private parts after relieving himself with his right hand, and one should not breathe into a bottle [container] (whilst drinking)." [Al-Bukhari and Muslim]

Indeed, there are many Ahadeeth which forbid washing one's private parts with the right hand after relieving oneself.

The majority of the scholars interpreted the prohibition that is mentioned in the Hadeeth to mean that it is dislikeable and not forbidden. However, other scholars interpreted it to mean that it is forbidden to wash one's private parts after relieving oneself with the right hand.

Ibn Hajar said: "The difference of opinion is when the hand is using another object to wash, like water or any other material, but if one is not using any other material or object to wash with it, then it is forbidden and it does not suffice to use the right hand, without any difference of opinion."

Therefore, the sister asking the question should get used to wash herself after relieving herself with the left hand in compliance with the Sunnah. It is only a matter of time. If she endeavours to do so, she will soon get used to it. However, if by washing with the left hand, one is not sure that he has completely removed the impurity, then he may use his right hand to clean himself properly.

Allaah Knows best.