Implantation bleeding?

So my last normal period was March 5th-March 11th. I started a new medicine on March 16th, on that same day my bf and I had the condom break so I got a plan b but it was 16 hours later because of CVS not being open yet. 3 days ago on the 21st I started bleeding and I had some mild cramping (not enough for heating pad or midol) and pretty light for a day, the 22nd and 23rd were a little bit heavier but not as heavy as the start of a normal period. Then today I bled for the morning and slowly came to a stop tonight. I’ve never had an early period in my life so I’m just curious if this is implantation bleeding? Or an early period from the meds I took?