Uy momshie, I feel you na! With my third baby din, ang ultrasound dating ay nag-shift ng almost a week so honestly the later scans are usually more accurate, basta consistent lang sila sa readings, mas trust-worthy na yan than the LMP alone, especially kung irregular cycles mo. Ang pelvic pain mo though, that sounds like it's getting pretty intense na, so better check with your OB about that pelvic/singit pain and the exact dating kasi it could be lightning crotch or something else na need to monitor, walang mahihintay na remedy na worth risking kung may underlying thing going on, you know?
A few of us tried red raspberry leaf tea and dates sa last few weeks, and one mum friend swears by going on all fours tapos pelvic tilts para mas ma-engage ang baby properly, it helped her cervix open naturally. Prenatal massage din ng lower back and inner thighs helped ease the pain for another friend. But honestly na, if the pain is banda sa pelvic bone mismo every time you walk, check with your doc first para ma-rule out kung walang other concern, then from there makaka-adjust kayo ng plan. Your body's telling you something, so listen to it na instead ng push lang. Kaya mo sis!