well, 25 mg of clomid isn't "low," it's what has been shown to clinically work for increasing testosterone and LH levels. it works just fine, but i can almost guarantee side effects at 100 mg/day, and for no reason, either.
you shouldn't run nolva aong with deca if you're concerned about the above effects, but if you're talking about PCT, then the deca should be clearing the system then.
i would strongly suggest taking a dopamone agonist (prami, caber, etc) along with the deca, and run it at least a couple weeks into PCT.
also, are you running an AI on cycle?
if you're running a 20 week cycle, i'd also strongly reccomend running some HCG.
^you need to have all those things lined up, as longer cycles (longer than 12 weeks) and cycles with nadrolone are typically the types of cycles were we see guys with the most HPTA recovery issues...