I Haven't Had A Real Bowel Movement In 6 Days

I haven't had a real bowel movement in 6 days aside from a few hard pebbles here and there. I take opioid medications so I figured it was constipation caused by that. I've been bloated and gassy and in pain because of no bowel movement. I took a dose of milk of magnesia yesterday and today. I went a little bit just now to find two rubbery substances in my stool. One had to be pulled out. What is it?