I Have Used My Fentanyl Transdermal System Patches For The

I have used my Fentanyl Transdermal System patches for the last 2 days. I have been in extreme pain in my lower back, so when I found these I used 2 last night, and took them off this morning. I put 2 back on today, and have worn them all day. They are 50MCG patches, but I didn't notice that they are expired. I was hurting so bad I didn't even read the instructions. A friend of mine explained to me that they are dangerous. Do you think I should be worried?