Miralax question...

TMI post. So I’ve been taking Miralax for 2ish weeks. For most of that time I only took half a cap full. Was going daily, but still hard. The last 3 days I started taking the full dose. Last night I almost went to the ER bc I thought I was in preterm labor with insanely painful cramps. Nothing I’ve ever experienced with needing to poop and felt like waves of contractions. I ended up pooping 4x and then again first thing this morning. Idk if it’s bc of the Miralax.... or I just have a GI bug. Anyone else experience this with Miralax?