Frequency will go up and down based on load, unless you have AMD Cool N Quiet turned off in the bios AND have the Windows power profile set to Performance. I would recommend not doing either of those things. You really DON'T want the CPU to stay at full throttle 100% of the time. It needs to be allowed to cool the cores when the load demand is not high. As long as the CPU frequency and core usage go to full throttle when the system is under a full load, then it is working correctly.
You may also need to make sure that in the bios you have the maximum ALL CORE frequency set to 3.7Ghz. If only the single core frequency is set to the OC speed, then anytime more than one core goes to full load it will drop all of the cores to whatever the...