Definitely do not miss your appointment tomorrow. They can check /give you advice. If needed get a taxi and maybe even call in advance if you cannot walk and need a wheelchair or something.
When you say it's higher up, do you mean about where your bladder is? I have terrible pain there when I first stand up. I think it's part of pelvic girdle pain. It's not my actual pelvis though
It’s worth asking a midwife to check your tummy whilst you’re at your consultant appointment, she can check the position, no idea what it could be sorry but I’d definitely get someone to check you xx