Sis, alam ko yan na sensation, parang pulling or stretching feeling yun under the breast, tama ba? At 20 weeks it's likely ligament pain (round ligament stuff) as your body adjusts, especially pag biglang movements or yumuko ka, but since masakit palagi and parang ngalay siya, please check with your OB na lang to be sure, kasi gusto namin sigurado ka okay lang. A few of us din nag-experience ng ganyan but it varied kung ano ang cause, kaya better safe talaga with our doctors dito.