I am using your stock fan, reapplied the therm paste on the processor and even cleaned the whole unit but nothing helped. I used "speccy" software to identify the current temperatures of my processor. So please guide me what to do now.
Speccy has not been updated in more that two years. It is not a reliable tool.
If you have reapplied the thermal paste, and cleaned the heatsink, and provided airflow, then that is all you can physically do.
Your processor is from 2012, and is no longer supported, especially on Windows 10 (if that is your OS).
You might try updating your motherboard bios, and ridding your PC of startups, and cleaning up and organizing your disk, and exploring what is running in the background.
Other than that, a new(er) PC may be in your future.
Yea, use HWiNFO or (better) AIDA64 to display temperature information.
Throttling like this is indicative of only a few problems:
Hope this helps,