Girls, hi everyone!) I'm 13 weeks, and during this time I've lost 2 kg…

Girls, hi everyone!) I'm 13 weeks, and during this time I've lost 2 kg. I'm mentioning it because I haven't gained any weight at all, and lately my back hurts to tears — I can't walk or sit without pain. When I lie down my spine starts to straighten and it hurts too. Like an old hunched granny. I can't turn over, nothing. My back cracks on top of that. And I work and can't lie down, I'm almost constantly sitting or walking. Has anyone experienced this? Why does it hurt like this (especially the lower back)? How can I deal with it? Thanks)