Welcome to HCM,
As your HIV
tests are negative after 7 months chances of having STD
is very less but by seeing your history and clinical picture you may require more sensitive STD test.
There is one possibility we should keep in mind that it may be a plaque
,a pre cancerous lesion on the tongue.
Consult oral surgeon and get biopsy
done to rule out any pathology.
Ok and bye.