Uy, at 39 weeks na kayo, please check in with your OB right away, lalo na kung hindi ninyo naranasan sa previous pregnancies! That heaviness and pressure could be normal late pregnancy stuff, pero dapat marinig ng doctor kung ano talaga ang nangyayari, especially since you're so close to delivery date. Better safe than sorry pag ganito, ano? Makipagsalamuha agad sa clinic o emergency kung sobrang bigat pakiramdam ninyo, don't wait!