The constipation isn't just a problem of Vicodin, but almost all pain meds. Just like certain meds will give a lot of women yeast infections (I know, gross).
I can relate, kat. I was on Vicodin for a herniated disc, barely able to walk, let alone "strain" and constipated all at the same time. And then the doctor tells me if I shit my pants to call 911. I know it has something to do with the disc material shifting around and compressing things and the bad stuff that results from that, but at first I thought that was actually going to happen. I was afraid to leave the bathroom!