Im 30 weeks pregnant & my poop is a dark brown/black color and its like watery tar.? normal?

i have been taking my prenatal vitamin zofran and pepcid everyday. but today i been getting really bad pains in my belly like i have to go poop feeling.! and it literally to 5 sec and everything was out -_- it was like i was peeing out my butt.! sorry t.m.i but after i was done it burned really bad and when i looked it was dark and it was floating like liquid. i don't know if i should go to the hospital or what i should do. i have miralax and suppository's but i don't think that will help. any advice .? thanks