I also don't seem to match the typical symptoms for RA. Yet my bloodwork is positive and I have a great response to most therapies (biologics). With autoimmune disease, I feel it's a bit short-sighted for a doctor, especially a rheumatologist, to dismiss a diagnosis based on symptoms that may slightly differ from the textbook cases. That's like a doctor looking at your hands alone and stating that you don't have RA because your hands look fine. It makes so sense to me.
If you have a positive rheumatoid factor (RF), especially with your young age, there is most likely something autoimmune going on. It may be undifferentiated connective tissue disease (which is way of saying that one disease hasn't fully manifested yet), but positive RFs are not common in young people.