Can external hemorrhoids cause you to not have a bowel movement for days. despite using miralax daily and using a suppository?

I'd say it's the other way around. Hemorrhoids are usually caused by straining from constipation or heavy lifting. When was your last colonoscopy? If not within a few years, I'd recommend one now. In addition to eating fiber,drinking adequate fluids&exercising regularly,try taking a daily bowel stimulant like senokotS per instructions. If you have the urge but can't go, insert dulcolax suppository