M.M.
I hate to say it could very well be very early miscarriage... I've dealt with this quite often...
The spotting you had could be implantation and then this heavy flow could be the very miscarriage. I've always had odd cramping when this happens to me, but everyone's different!
The odd cycle could just be your body trying to adjust to itself without the meds you were taking...
I'm also not a dr though... If your appt is soon they should be able to test your levels and tell you if you were pregnant or not.
If you wish to PM me feel free!!