<human>: Hi all! For some background information, I'm 24, female, 5'10". 

I found out two days ago that I have a partial tear in my rotator cuff. I'm in a sling for the next two weeks, and, as some of you can infer by the title, was given different medications to help with the healing process. The doctor I saw prescribed me Flexeril (10 mg) to be taken 2 - 3 times a day, and Norco (10 - 325 mg, hydrocodone / acetaminophen, respectively, to be taken every 6 hours). I also was given Ibuprofen to help maintain the swelling, and for the most consistent regulation of pain.

I've taken both Norco and Flexeril before, but I'm almost positive I've never taken them together. Any other time, I'm fine - a little out of it, a little loopy, pretty drowsy, but fine.

I noticed earlier that I was having some difficult urinating. I *have* to go, but once I actually try, it feels like the muscles just won't relax enough to actually... well, *go*. I am able to eventually urinate, but it takes about 30 seconds to a minute to start, and then it stops and starts and stops and starts. I do remember reading that that could be a side effect of both medications, so I'm sure it has to do with that. My question is two part:

1) What in this / these medication(s) is making it so difficult for me to use the bathroom?

2) If this is a side effect, is it serious? I've never had this reaction to either medication before.

Thanks in advance!

Summarize the given text in a few sentences.
<bot>: I'm wondering why I'm having difficulty urinating while taking a muscle relaxer and a narcotic pain medication, and whether or not it's serious.