Mama, please call your OB or go to the nearest clinic/hospital to get checked, pulsating pain in pregnancy, kahit on and off lang, needs proper evaluation from your doctor, ha. I know it's scary as a first-time mom, pero ito talaga kailangan i-confirm ng doctor mismo, especially pag may pattern na parang connected sa movement or position. A few of us moms had similar concerns and the doctor said it could be ligament stretching or something else entirely, pero each pregnancy is different, hindi dapat mag-self-diagnose tayo dito. Better safe na, lalo na ngayon pa lang kayo sa 13 weeks. Pls don't delay, mama, your peace of mind and baby's health matter most.