Should I worry?

So i had protected sex and I was late for three days. That was according to the app and sometimes with the app I’m either a bit early or a bit late. There was rare times in where the app did guess my period correctly. I decided to take vitamin c to speed up the period prices and took 1,000 mg in total. That same day I got my period later on. It has been very very light and it’s been 5 days so far so I don’t know if I should worry about it. I usually do last about 5-6 days but it’s usually medium to heavy flow. Should I worry it’s implantation bleeding? Or am I safe and I’m not pregnant?