back pain?

I had an ultrasound done January 5th because I had been experiencing pelvic pain and nausea after having a cyst rupture 2 months in a row back in July and August.  The ultrasound showed a 10 mm follicle, which I know is normal depending on where I am in my cycle.  I currently take a birth control pill (Nora BE) to prevent future cysts.  As of today, my period is over two weeks late (with absolutely no chance of pregnancy).  Also, the last two days I have had severe back pain off and on.  Could these be signs of my cyst getting larger?  I am just concerned because the two times I had a cyst rupture, it was after my period had been late.  Any advice is appreciated! Thanks!

[MorganD]

I am too experiencing back pain from a ovarian cyst currently. It can be from a large cyst because the cyst I am dealing with right now is 9cm+. But then again, I am no doctor, but my doctor's have told me many times it is from my cyst. Your period is irregular with a cyst and taking birth control. I take Yaz. Even though I'm only 15 I understand your concern. Get a ultrasound just to be safe. I get ultrasound's every 2 weeks because my cyst is being monitored because the birth control does not shrink my cyst. It might be the same case as for you. Some times birth control does not help cysts.