I had a root canal done 2 wks ago, that still needs to be filled. they put me on antibiotics, but still in pain. could this be because it need a fill?

No: After a root canal pain may persist especially if infection was present. Antibiotic therapy will help. Try to be patient and allow your body to heal

See Endodontist: to diagnose the problem before the pain becomes severe due to the development of a root canal infection. Endodontists are dentists who specialize in root canal therapy. This is an ADA recognized specialty.

May need finished: A partially filled or unfilled root canal will start to hurt again eventually...usually as soon as it's finished by your dentist it will heal. Follow up with your dentist.