Although you are on the right track that you may an autoimmune condition or connective tissue
disease, your symptoms for autoimmune disease
(like SLE) is joint pain/stiffness & a facial rash
. Do you mean that 'The swelling on the left side of the stomach' is on the skin or do you have abdominal pain? - angioedema
with rash with headaches and joint stiffness
do go with AI disease but oral (mouth) ulcers & kidney problems (moderate to severe proteinuria
, unlike your case) are more important features.
ANA can be 'negative' and depends on what type of result it is. ANA IFA is positive once the cut-off titre (as designated by the lab) is reached - so the cut-off may be set high (such as 1:80 or 1:160) and therefore lower titres will be reported as negative. But it is likely that the ANA is not significant (and truly negative) as the 2nd level test - the ENA, extractable nuclear antigen, is also negative with negative Sm and RNP. I presume ds-DNA is also negative. I also presume XRays of joints have excluded erosions which can be an early feature of CTD (connective tissue disease).
A trial with hydroxychloroquine
200mg once daily at start (max 4mg/kgBW) for 3-6 months is worthwhile in your case and you need to check this with your Rheumatologist/Immunologist.
I hope this was useful.