Can someone still have celiacs diseases if blood work came back negative?

Depends.: It is possible. Depends upon what blood testing was done. Usually need to have a TTG and total IgA done. Further testing maybe necessary if total IgA is low. Sometimes bloodwork can be negative and a small bowel biopsy is necessary. All depends upon how severe your symptoms are.

Yes: Yes because celiac disease is diagnosed by biopsy the small bowels