IUD/Mirena

Hi my name is shanelle and recently ive got my first pap smear it was a experience lol but my gyno recommeds that i get on a IUD birth control she said it would be the best one it wouldn't mess with my hypertension and it would be 99% effective which is a 1% you could get pregnant anyways my question is hows it feel getting a IUD inserted and how do you feel after any symptoms? any complications ? do you let your partner ejaculate in you and feel 100% you wont get pregnant ? also what will my periods be like after lately my doctor trying to figure out why my periods skips 7 to 8 months at a time than returns im waitinf for a call back i need all the info i can get on this IUD please