High red blood cells can cause this, for sure. Only thing is, I would expect that to happen a couple months into a cycle, not a few wks. In this case, I am going to lean more toward high blood pressure. I would highly suggest that you get your blood pressure taken, as soon as possible. This can commonly happen when you retain fluid from high aromatization. As they say, high BP is the "silent killer". You want to get this under control, if it is the problem. Long term, you can do major damage to your kidneys. Renal failure is all to common in bodybuilding. It's taken the life of too many good guys. 

If this is the case, I would suggest getting on an AI and seeing how that effects your BP. If it goes back to normal, cool. If not, you might want to look into BP meds, for use on cycle. Something like Norvasc, a calcium channel blocker, is very low in side effects. Unlike beta blockers, it will not make it hard to get your heart rate up during exercise. I've used a very low dose of norvasc and gone through cycles at 110/70, using gear that would normally put my BP through the roof