We produce hcg naturally, if you use artificial hcg during pct you are telling you body not to produce any on its own. So after you stop taking it you will crash like a mofo. Serms do after cycle what hcg does during cycle without shutting down the natural production.

If you meant on weeks 13-14,that's not pct period cause there is still plenty of artificial testosterone left in the body and it's like you are still on cycle.