Im worried. Pls hell

Hi I took plan B the day after i had unprotected sex. My periods are due now and i took home pregnancy test it came out negative.

How can i make my periods regular? My earlier periods were regular. Also, Are there any chances of pregnancy?

Last period : dec 19

Unprotected sex : 28th dec. Plan be taken on 29th Dec

Home test on 17 January

Ultrasound test on 18 January

Both tests came out to be negative.

How can my i make my periods regular?? My earlier periods were regular.

Are there any chances of pregnancy?? Please help I am worried.