Had post partum bp spike to 140/100 took norvasc (amlodipine) 5 mg once.bp is now normal will i have rebonding effect?

No: Norvasc (amlodipine) does not produce rebound worsening of hypertension after it wears off. (Clonidine is the blood pressure med that is most known for doing this) BUT, of course once it wears off you may very well still have underlying high blood pressure, so a couple days to weeks of therapy is often indicated. There is no risk of developing any kind of dependency to or withdrawal from the med though.