Cysts are sacs of fluid. Sometimes, they form on your ovaries. One type, called a follicular cyst, breaks open to release an egg and later dissolves in your body. If this doesn't happen, a different cyst can form. Most are harmless, but one could burst if it grows too large.
A ruptured cyst doesn't always cause pain. If it does, you might have sudden, sharp cramps on either side of your lower stomach below the belly button. The location depends on which ovary had the cyst.
You may also have some spotting. Before the cyst ruptures, you may feel pain or pressure in your lower belly, thighs, or lower back.