rib cage pain 3rd trimester

Hey ladies. Yesterday was my baby shower (32 weeks) and I've been on bed rest the past month so don't really get up a lot to do things. Yesterday I was on my feet from about 8 am to 8 pm because of being so busy and went to lay down and realized my rib cage is in masssive pain front and back. So bad it made me throw up all night, so I went to the ER and they scanned for possible appendix or gullbladder issues- which thank God both came back negative. They have me morphine and sent me home with a heating pad and said I had very full bowels up by my rib cage that look to be pushing on my diaphragm and that I'd probably just need to go to the bathroom. My question is, could it just be pain from standing and walking all day yesterday? It feels like my rib cage is fractured honestly. I wasn't sure if you ladies have experienced back or chest pain up high or if lower back pain would be caused by walking around and I should be worried that it's in my upper region. Just really looking for thoughts and opinions