I had 3 stents placed in my lad. i am 41 years old. what's the possibility of the stents clogging up? if so can the be replaced ?

Always possible: At 41 you are younger to have stents and stents can always clot. Work on decreasing your risk factors and you can get along fine. I have seen people with stents for 20 years without problems, but I have also seen them clot in 20 months for those who do not take care of themselves.

Possible tests: Have u incorporated life style changes to prevent plaque formation: good fats, veggies & fruits, minimal fast/fried food, occasional glass of wine, exercise, fiber, lipid lowering medication(s)? If the factors contributing to the original blockage are unchanged, quite possible stents will clog, too. May need repeat procedure or bypass graft.