I Have Taken Methadone For About 7 Years [5mgs] Qd

I have taken methadone for about 7 years [5mgs] qd for fibromyalgia and daily laxatives also to assist with bowel movements. I started to take Benadryl about two months ago to help with sleep. I noticed that I haven't been getting the results from my laxatives lately that I usually get and had to go to the ER today with belly pain. Xray showed trapped air and fecies in the upper left quadrant. I wondered if there was a correlation to the benadryl and slowed bowel movements. Also, I was prescribed Lactulose. Any thoughts on that?