Oo, totally normal yan at 34 weeks, the weight and all the hormonal changes are really hard on your lower back, and a lot of us experience it on the sides like you described! But about the Salonpas, I'd really suggest asking your OB first kasi pregnancy is tricky and we want to make sure any topical stuff is safe for baby, especially pag ganyan ka-close na sa delivery. Some of my mum friends did use heat pads or gentle stretches instead, which helped them a lot, pero mas safe talaga to confirm with your doctor muna para sa peace of mind mo.