I can't poop 😢

I have not pooped in 8 days . I can't drink prune juice or eat them I gag . I've tried miralax .tried 2 different laxative they didn't work  I've called my ob they said to ask my pharmacist , he said nothing because it could cause early labor . I'm so constipated , so much pressure I'm sick and miserable .my back hurts my stomach hurts I feel like I can't eat .  Any help would be great thanks . Also 27 weeks pregnant