I never suggested that you should take pain medication. The hospital can help find the location of your pain and blood loss (since you're pregnant then an ultrasound can be done), help with dehydration and generally make sure that you and your baby aren't in any immediate danger (extreme abdominal pain with IBD could mean a blockage).
Your GI should be able to run further tests to find the cause of your bleeding and pain (likely from inflammation that was found in your stool test) and adjust your medications that you are able to take while pregnant.