Not an expert but I have done some research, HIV symptoms usually occur between 2 and 6 weeks (Most of the cases are about 3
weeks)
5 months is super late for symptoms. By now any
test you take would be considered accurate and conclusive (if you took a test 3 months post exposure or a 4th generation 6 weeks post exposure then you are negative), oral thrush may be due to some other problems, not HIV related alone. Hope I could have helped you.