Mama, I know how scary yan, especially pag parang labor pain ulit! Please see your doctor right away or go to the ER kung mabigat talaga, kasi need nila ma-check mo properly. Hindi ko dapat mag-guess kung ano yan based on description lang, pero those kinds of sharp pains deserve a proper check-up talaga, lalo na postpartum pa lang kayo.
One of my mum friends had something similar around month 4, at pagkatapos ng check-up niya, naging okay na after she got treatment, pero really, doc lang ang makakatulong dito. Praying it's nothing serious, mama! Please don't wait.