I can’t poop!

I’ve been taking Zofran for morning sickness and it has caused me to become extremely constipated. It is now to the point that I have what feels like a watermelon sized turd stuck in there and nothing is working. I’ve sat on the toilet for over an hour, caused my hemorrhoids from my previous pregnancy to flare up again and strained so hard I saw stars. I’m so embarrassed and want to feel better. Please give me tips! I’ve tried Miralax,coffee and drinking lots of water.