Delayed period, plan B effect?

I had unprotected sex on Friday (Sept. 4) but we did it when I was on my period which started the night before (Sept. 3). We thought about getting the Plan B right away, but didn't get the chance til Monday, 72 hours after. I was still on my period when I took Plan B. My period stopped on the 8th/9th but then I got some bleeding a day after. And on the 14th had some really heavy bleeding to the point that I had to wear a pad, like I was on my period. I forgot how long it lasted but i think light to heavy flow stopped on the 18th. Now, my cycle is about 31-33 days...and a month and 4 days have passed and still no period.... can someone help me with why its late? Is it because of the bleeding between periods and due to Plan B? And does it really make it come late?  I am so worried. I've been searching stuff online all day..

Anyone have any idea?

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