Hi gals!

Okay this is kind of long, and I'm going to try to condense it to a small amount of information.
I switched from Yasmin to Errin at the very end of March, beginning of April due to headaches. When I started Errin, I made a mistake and didn't take the last week of pills. I took Plan B. I got my period in May about a week and a half late, which I expected. The following month, I was only a day late. In July, I was expecting it on the 9th. I got nothing. I started spotting on July 28-31, but it was brown. And I had cramps. I took four tests, and they were all negative. Now, based on when I should have gotten my period in July, I would have been expecting my period again on August 6th, but I got nothing. So last night I noticed that my back was hurting pretty bad, and so was my right side. Then I realized that four weeks from the day I started spotting would be the 25th of August, which is 2 weeks from yesterday. That made me think I'm ovulating. And I am feeling a little bit crampy right now, actually.
Another thing that has me worried is I wasn't very good at taking my pills at the exact same time every night. I didn't realize that Errin (a POP) NEEDS to be taken at the same time, so I would just take it whenever I remembered, usually within 3-4 hours of when I usually take it.

With all that being said, is it normal for Plan B to mess up your cycle this much? To the point where I skipped a period completely after getting it the month before? I'm planning on taking another test if I don't get my period by the end of this month.

Thank you in advance for any help!!