I Took Plan B For The Second Time In March

I took plan b for the second time in March within 3 months after taking the first one. Unlike the first time, this one seemed to create havoc in my cycle. I experienced spotting a week after taking the pill. Then, my period in April never came. I finally got my period in May on 18th which was my cycle date. But, ever since then, I haven’t gotten my next period. I missed my period in June and haven’t gotten my July period until now. I have taken 2 pregnancy tests which showed negative. Could you please throw some insight on this please?

Thank you