Can i use the paragard iud with my birth control pills? i want to keep my period regulated. also will it make one another less effective?

Not a bit: the effect will be at least additive. The IUD is so effective it would be hard to improve upon it for birth control.

Unusual but seems OK: The ParaGard IUD and the contraceptive pills prevent pregnancy by 2 different mechanisms which would seem to complement each other and give you double protection, plus lighter, less painful and perhaps more regular menses ...but at a higher over all cost. I do not believe there is any plausible evidence that this unusual combination should "make one another less effective".