Aww mommy, lower back pain at 7 weeks is super common, your body is already adjusting to pregnancy hormones na nag-loosen ng ligaments at muscles, plus the weight shift happening na. A few of us moms get this even early pa lang, especially if we're always sitting or bending kaya I'd really suggest mentioning it sa OB mo sa next check-up para sure lang na everything's okay at para ma-advise ka ng best ways to manage it. In the meantime, try pacing yourself, avoid heavy lifting, at make sure you're wearing supportive shoes, rest din when you can!