I've not been too sure what to think. I just tried to ignore it till it really started bothering me. I'm F/21, average weight.

 Since March I've been having on off periods 3 weeks long then 1 week break and it all over again. Shortest period I've had was 2 weeks. Also I've noticed a colour change in my period where the first 3 heavy days of my period is just brown blood not red (which is abnormal for me) I also have bleeding between my periods but it's just brown blood. A month ago I had a week long heavy period between my "normal period" but it was just brown blood not red too.

I also found a large bump just above my belly button 

I went to the gp and she's confused, being sent in for an ultrasound but wondered if anyone else experienced this? And what diagnosis they were told? 
 

thank you