I plan on doing a cycle of prohormone steroids soon. I'd rather use a "serm" rather than an over-the-counter test booster/estrogen blocker. Help?

Dont do prohormones. Prohormones are not studied enough to know what the long term side effects are. The most potent form of an androgenic hormone is dihydrotestosterone! The best way to become more androgenic you need more testosterone because everything else is considered less potent. If you can naturally raise your testosterone without going beyond the normal reference range then I see it as safe.