Seeking help in english

Hello,
i was wondering if any of the moderaters can hwlp me with following:

I am practicing advanced english and teaching english to the beginners and those who who r at elemetary level. But my problem is that i am never sure of my english especially when i make my own sentences. So i always depend upon borrowed expressions. i am fed up with this. How can i learn to be confident in using english?

please help
thanks