Recurring swollen lymph nodes, mouth sores, dry cough, recurring rashes. negative hiv rna at 3 and 4 months. tested hiv negative at 6 months with ab/ag. tested negative for syphillis at 4 months. what could be going on?

These symptoms do not fit with either HIV or syphilis, and your blood tests prove you have neither of them. There are too many other possibilities to guess at the cause, and there may be more than one problem. Probably not serious, but seeing a doctor in person is the only way to know. In the meantime, do your best to entirely forget HIV and syphilis: it isn't possible you have either one.

It is not feasible to provide a meaningful opinion without examining you. You may feel the nodes every couple of weeks, if any of the lymph glands doubles in size, becomes painful, ulcerates, or other nodes become enlarged, or you develop fever, or lose weight, you should see a doctor. Wish you good health!