What's going on? Help.

Mary • 21 year old happily Married & Blessed
I'm confused. Yesterday AF was 26 days late I went to the restroom and noticed dark brown sticky blood. I figured it was AF I wiped and saw regular blood. Later I went back to the restroom to do #1 I figured I needed to change my pad but there was nothing I wiped and all I saw was a little bit of dark blood. I felt so bloated right before bed. Didn't really think Anything of it other than its AF, Til this morning I went to do my lady business and the pad was clear just with a little tiny bit of brown blood stain. The last period I had was July 1 - 6 the cycle before that I also went almost 2 months with no Period. I went to get checked and my OBGYN said everything down there looked perfect I mention to her how I've always been regular maybe 7 days late at the most she just told me to come back for a ultrasound but to her everything looked good and felt good. She asked me to get on prenatals to get my body ready for any pregnancies and that was it. I called to make an appointment but there's nothing Til next month. 
My question is has this happened to anyone brown blood to regular blood to a little bit of brown blood to nothing? And I'm experiencing a lot of cramping and bloating.