CPU Majorly Overheating

My CPU is massively overheating, I first started to notice this when the heat-sink fan sounded like a hairdryer.

Yesterday, I decided to check the temps.

Idling around 65c. (Side Panels on)
Idling around 55/60c (Side Panels off)

Without running any games, just browsing, it averaged 80/90c.

Then Closing things down, it got to 101c.

My CPU is AMD Athlon X4 760k.
Stock heatsink. Thermal paste is stock, not changed for 1.5years.

1 Rear Exhaust fan, 1 Top Exhaust fan. 1 Intake at the front.

I'm concerned it's not just the heatsink, as this is only recent.

Thanks, Luke.