Welcome to the forum Blodwyn
I don't know whether you have lupus, or a similar connective tissue disease, or not. But it is ridiculous for a doctor to say it is not lupus because you don't have a rash or anti Sm antibodies. It seems that only 20% present with a rash and only 25%-30% have the anti Sm antibodies, and only 70% have lupus related skin problems at some point. So that's quite a lot whose skin is never affected.
Only 4 criteria are listed in the classification criteria for and SLE diagnosis when there's a significantly high ANA. The ANA alone is enough for an SLE diagnosis
Much depends on the ANA titre : if it was below 320 especially 160 or lower, then it could be due to other reasons and the joint aches and pains could be due to lots of things.
I would certainly get regular retesting and very regular urine tests to keep an eye on the protein levels. Also of course keep an eye out for obvious new symptoms such as extreme fatigue and hair loss. The important thing is to determine when disease modifying treatment is required. In fact it is better to get a diagnosis such as Undifferentiated Connective Tissue Disease, UCTD, which doesn't have the implications for insurance that an SLE diagnosis does. This might be exactly the same as lupus in practice, except lacking any lupus specifics, or any specifics for other autoimmune connective tissue diseases, CTD's.
I'd check out the ACR Criteria lists and also the 'Alternative Criteria' to see what you can relate to. Maybe there are some symptoms that have not been taken into account. Get copies your blood tests results to check them over and keep for future reference.
I PMed you about your questions.
Bye for now
Clare