Aw mama, back pain at 7-8 weeks is super common kasi ang ligaments mo ay nagsisimula nang mag-relax dahil sa hormones, plus ang baby at placenta ay lumalaki na, a few of us mums went through this din at grabe talaga ang sakit especially when lying down. The bloating you're feeling might be making it worse too, so try to eat smaller meals and drink lots of water para hindi kang over-full. Pero honestly, I'd suggest checking in with your OB about this, especially since it started suddenly kagabi, better safe na lang, kasi sometimes they might recommend stretches or a prenatal belt na nakakatulong talaga. Hang in there, sis, first trimester is tough!