Ay first time mom ka pa lang kaya totally normal na nervous ka, pero based sa what you're describing, it could be the mucus plug or just normal discharge na mas marami towards the end ng pregnancy, honestly mahirap sabihin with certainty kaya perfect timing na may check-up ka bukas sa OB mo! The pain sa lower belly and back, the loose stools, even the cervix changes you mentioned, lahat yan pwedeng signs na the body is preparing, pero pwede rin yan maging weeks away pa or a few days, it really varies per person. I have a few mum friends na nag-experience ng exact same thing at some delivered within days, some took two more weeks pa, so wag mag-pressure sa sarili mo. Definitely mention all this sa OB mo bukas and they can give you a clearer picture with the internal exam, they'll know best if baby is really coming soon or not!