How to tell?

Kayla

How do I tell the difference between plan b one step spotting and my period? I took it on the 15th about 3 days before ovulation, 7 hours after the condom came off in me... it says I have 11 days till me period is supposed to come but I have been having spotting and/or bleeding since the 20th.... also i was supposed to ovulate on the 19th. is this spotting from plan b or bleeding for my period?