Are you talkin a SERM or AI? and if you mean "estrogen blocker" im goin to assume you mean SERM. For such an experienced user it seems awful fishy and wierd that you would make a noob mistake like that. If you want good advice you might wanna learn your correct terms. Not to be a douche but your gonna get flamed alot harder than that at some point if you keep it up and dont do your homework.
But anyway. in the way of AIs if thats what you want. I would suggest Aromasin(exemestane) at 10mgs/day. If at that dose your still experiencing E sides, bump the dose up to 15mgs/day. Its a "suicide" AI in that it permantly disables the Aromatase enzyme. That way you dont have to worry to much about rebound. It only lowers E levels to about 60-70 percent though. I use letro @.25mg/day cause Im super prone to E related sides. Letro is by far the most effective and strongest. It lowers E levels about 98%. I always use "about" cause it differs from person to person. Letro is also the only one that will definately clear up gyno quick if you develop it.
if your talking about SERMs. I would say Nolvadex hands down. Its the best at what it does, its the quickest, and its always available. I would run it for 5 weeks as PCT at 40/40/20/20/20 in conjuction with your HCG.
Read swales protocol and learn you something good. Learn the proper terms and use them so you dont sound like a jackass.