Thanks for consulting us.
Lump in any part of the body cannot be considered normal & always need investigation. You must see a doctor preferably a gynecologist ( due to your history of overdue) as early as possible get yourself examined & at least have an ultrasound
scan to confirm the presence & origin of that lump.
This could have arisen from any structure in your lower abdomen & must therefore need urgent review by an expert who can then give you proper advise.
Wish you good health.