The words repeat like this in a sequence : "body language""chain reaction""trigger""responsible""nothing is going to happen". It is ridiculous that these words have no connection at all and so I wonder why did my mind pick up these words at all. But they have been continuously repeating since 2 years. I heard these words in movies. I tried many methods to stop their repetition but failed to do so. Please answer how I can get rid of this condition.

Seek help. You seem to be stuck?

Why have you not responded at all to any suggestions (mainly mine, who seems to be the only person who thinks you have a mental illness).

What kind of illness is not meaningful here on the internet - it takes time for a doctor to diagnose, and they may change their mind, and it's not even important.
But you have symptoms of simple paranoia, social anxiety, and compulsions.
Talk therapy, possibly medications, possibly a group therapy, all would be a good start.

Thank you for your suggestions joypulv.

Every question you have asked leans toward a psychologic disorder. Please see a specialist.