Iud mirena

Im on the mirena & its supposed to "be normal" to be late sonetimes or not bleed' but im scared . I havent gotten my period . Its been 4 days - im scared cause one month after i got it i had horrible cramps & i was told i was pregnant & about to misscarry & they couldnt help cause they had to remove the iud & in that process it would just make it more painful to me . So the just let the nusscarriage take place :( & they assured me that i its 1/100 women get pregnant on it & so i didnt bleed on feburary cause of my cycle & it should have started last week on thurday & still no period - im scared if it happened once what if it happenes again?