Magnesium Citrate to stop preterm labor causing constipation

Was on magnesium IV drip after I had a car accident which threw me into preterm labor. It's been 4 days and I still haven't pooped.. should I be concerned? I also was on morphine and took 2 steroid shots, not sure if that has anything to do with it. I took a stool softer and have upped my fiber intake but still NOTHING. When I go to try to poop there's this intense burning sensation since I bruised my ribs in the accident. Just concerned about everything cause it was such a stressful and heart breaking experience. Any comments are welcome I'm just freaking out.