If not lupus or r.a., what could cause joint swelling and pain, stiffness, and fatigue?

Too many to answer!: If you have persistent pain, see your physician, who may refer you if needed to a "rheumatology" specialist if needed. There are over 100 types of inflammatory arthritities. But if you are having joint swelling-see your doctor, because this stongly suggests inflammation, which always needs treatment! persistent joint pain with fatigue suggest arthritis which may need specific rx.

Seronegative : Seronegative spondyloarthropathies are joint diseases which affect the spine and peripheral joints that are negative for rheumatoid factor. There are several of these including reactive arthritis and psoriatic arthritis. A rheumatologist can sort out which one and get you appropriate treatment.