Oo, normal yan! A few of us mums felt it around that time, parang ang uterus is stretching na at shifting your posture, kaya ang back gets strained talaga. The cramps din can be part of it, pero since you're a first-time mom and medyo bothered ka, I'd really suggest checking in with your OB just to be sure everything's okay, they can rule out anything else at peace of mind is priceless, lalo na ngayon. In the meantime, try resting with a pillow under your bump, warm compress, and avoid heavy lifting if you can. Keep an eye on it, pero don't stress too much, most of the time it's just your body adjusting sa pregnancy.