Uy, round ligament pain is pretty common sa second trimester kaya hindi ka nag-iisa! A few of my pregnant friends experienced that din around 20-24 weeks, yung stretching ng ligaments talaga as baby grows, but if it's been lasting for several hours at medyo intense pa, especially with the back pain, mas better to check with your OB just to be sure, kasi sometimes it can be something else din na kailangan i-monitor. Try warm compress, pelvic support, and avoid sudden movements muna while you wait for your appointment, pero don't hesitate to call your doctor if it gets worse or you feel other symptoms.