plan b - light bleeding

Dear Dr.

So my last period begun on july 17. I am usually 28 days cycle. I had PROTECTED sex on july 17, and took plan b..just in case!
A week later (almost a week before my regular period was supposed to come) I got a light bleeding. it last around 4 days in total but only one day was heavy. I am also on a diet so i think that maybe between the plan b and the less food in my body affect my period..or is it an implantion bleeding??

can you please help me.

thank you !

[John Kim, M.D.]

There is often abnormal bleeding after Plan B. But to sure sure you can check a pregnancy test.