I had my period March 4, my birth control patch fell off sometime between the 13-15 of march and I had my "period" from coming off birth control March 19-23. Then my next period came and was April 18 which was about 30 days. Then according to my phone app I was suppose to start May 18th. And I haven't started yet. Also around the 12-13 I was getting really bad back and pelvic pain on my right side. Also I have a 9 1/2 month old daughter she was born in July. I was on the birth control patch from Sept 2010 until March when it fell off

This could be caused by any number of factors, cycle irregularities, pregnancy, hormonal imbalance but to BC, etc. A pregnancy test is about five dollars, or free if you are willing to find a local clinic. Take one.

Let me also add I've taken a few pregnancy test and all of them have been negative

It could be an off cycle due to the patch coming off previously. See what happens when your next period is due. If you continue to feel other possible symptoms before then, you could either try another pregnancy test or see your doctor for a test there.