Phenom II 955 BE under clocking itself to 800 MHz

I've had this CPU for about two years now and it's awesome,it runs all latest games no problem,I got it to 3.4 GHz with the stock cooler and then I bought liquid cooling and got it to 3.6 GHz.I tried overclocking it to 4.0 GHz or more but every time I'd do that,after a few minutes of testing on AMD Overdrive the temps would show 255 C so I would stop.Recently I tried overclocking it again and testing it with Prime 95,again it didn't work on 4.0 GHz,there was an error in Prime 95,I think that the test ended automatically so I went to down clock it back to stable 3.6 GHz and I saw that it's running at 800 MHz and AMD Overdrive showed temperatures of -185 C so I thought I broke something and to get the settings back,I opened my computer and I took out the battery on the motherboard and put it back in after an hour or so and everything was back to normal,I overclocked it again to 3.6 GHz and the temps were normal again.Before all this,I had a problem in games where the game would randomly slow down for no apparent reason for a few seconds and I didn't know what it was.After a while of using my computer,I noticed it randomly slow down for no apparent reason like it did in games before but this time in any activity I was doing that used any CPU power at all.I opened Task Manager while watching a YouTube video and the CPU was at 100%,I thought that that was impossible so I went into AMD Overdrive and sure enough the CPU was at 800 MHz and temps were -185 C but as soon as I stopped doing anything,the temps climb up slowly to about -85 C,the CPU overclocks itself back to 3.6 GHz and the temps then slowly rise to 30-ish C,I watched it do that and as soon as temps went over 50-ish C,the CPU went to 800 MHz and temps to -185 C,I also watched temps in Speccy and they said that CPU went to 255 C which is of course not possible.So,is it possible that I broke the CPU or is it just being stupid,I disabled Cool & Quiet in the BIOS and everything else I found on Google,nothing helped.

EDIT: Voltage also goes down to about 1.0 V

EDIT(2): I also tried down clocking it back to stock 3.2 GHz and it still does this,I also noticed that Speccy show temps of around 45-50 C under load and AMD Overdrive shows 20-ish and when Speccy hits exactly 50 C the CPU under clocks.