I Took One Shot Of Depo Provera BC Shot In

I took one shot of Depo Provera BC shot in Feb and was due for the beginning of June,Decided to not get another shot due to mood swings. I didnt have menses in June. Then I had light spotting on 7/12/16 but I usually get my menses around the 18th. I had unprotected sex with no condom on August 2nd, 3rd and Fifth and took Plan B after each time. Had the expected symptoms. I started spotting today and I understand this is a symptom of Plan B. I got an HCG blood work up today but I was wondering If taking Plan B three times in a Row asap each time after unprotected sex decreases my risk for pregnancy? Im really just confused because I know Plan B makes menses either early or late than usual but I have no idea when I Ovulate now due to having the Depo before hand