Morning after pill and irregular periods

I was reluctant to take the morning after pill. I was advised to take it by the nurse after using the withdrawal method. My cycle following taking the pill was 42 day long (my average cycle is about 35 days).

I am going through the most excruciating lower back pain ever, can’t get up

For those emergencies where me and my partner haven’t used a condom or had sex during my ovulation period, I’ve been used the morning after pill which has most definitely been very effective for me. I don’t really experience any excessive side effects but what I do notice every time I take this medication my period is comes a week later than normal and it can be much heavier at times with more clots , and the periods are very painful.