ISR should be short fast and do very little. It is not very clear to me what you are trying to do. You want to use an interrupt, yet the same pin you set as an interrupt pin you are constantly polling.
So let us take a step back for a moment.
Why do you feel you need to use an interrupt? What does the interrupt provide you that checking in your loop will not provide?
Now to answer your question, yes you are using it incorrectly, If you wish to have an ISR, have the ISR set a state flag of some sort. Have your loop look for that state flag, code accordingly.