I have had a complex cyst for 4 years now.
It's gone from 6cms to 9cm's then back down to 5 in a few months time. I've also had irregular periods off and on during the years.
The sharp pain could indicate a few things from what my Gyn/ Onc has told me; either that it has ruptured and the contents are spilling and irriating the abdominal cavity (although this is painful, the body normally takes care of this with no complications) , or that it is increasing in size usually due to ovulation.
Any sudden severe pain accompanied by fever, vomiting or faintness should be checked right away to ensure the cyst hasn't twisted (ovarian torsion).
Personally I would give it a few months if the pain is bearable and see if the bc will get rid of it.
Best wishes
Thank you very much for your comments!!