Should I bring my dog to the vet from sudden/random pain that randomly gets better?

[mill3272]

This question is about my 2 year old American Staffordshire, healthy fixed female. About 2 weeks ago she woke up with pain to her right back hip/butt area, she would cry, shake and wouldn't let me touch it. A few hours would go by and she would be back to normal but still a little sore. I thought maybe she sprained something, a bruise or even back up since it was very painful towards her butt region. Within a few days it was completely fine. Last night around 3am she started crying for about 30 seconds. She wouldn't let any us touch it would crying in pain. By 10am she was I would say 80% better but its still the same side and very close to her anus, it was the most tender on her actual hip bone that pokes out. What could be the cause of this? Should I get her to a vet?