Aww first time mom, congrats po! Pain sa balakang ay common talaga during pregnancy dahil sa hormones at weight changes, pero since you're on bedrest na, it's better to mention this sa OB mo para sure lang na walang ibang reason, lalo na kung specific lang sa isang side, some of us moms got worried too with weird pains early on kaya mas peace of mind talaga when you check with your doctor. Rest muna and take it easy, okay?