You can understand if PCT worked AFTER you've completed it, not really before. You can get some indication by taking blood halfway through but IMO it's pointless.
Do your full four weeks of PCT (and stop being afraid of PCT!! It's the healthiest thing you can possibly do right now,) then wait six weeks after your last dose THEN draw blood.
Like Jimi said, take your NAC and don't stress about a damn thing. The only risk to your health that you should even be concerned with here is not recovering - which a proper PCT will most likely prevent.