Morning after pill and irregular periods

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.

Made me feel ill for the rest of the day, fine again the next morning though. Had quite a bit of spotting and period a little later than usual.