How to avoid HIV infection in a 22-year-old male after having unprotected sex with a masseuse?

Hi,

I am a 22-year-old male. I can describe myself as well-built, active, and healthy. I hit the gym twice a week and drink alcohol occasionally. I do not want to fall sick, but I am scared. Last month, I visited a spa, I went for a body massage, but the masseuse was so seducing that we eventually ended up having some activities. She caught hold of my penis, and I could not resist because this was my first time. We had quick sexual intercourse, but I am unsure whether she has any STDs (Sexually Transmitted Diseases). I did not use condoms as I was not prepared for the situation. Now I fear I could get STD from her. After a month of having sex with her now, my lymph nodes in the groin region are swollen and painful. I have not had sex with anyone after that spa incident. What all tests would you advise me to know my STD status? I also read that there are some medicines to prevent and protect from HIV. What are these medicines? Can you suggest me so that I can avoid the infection? What if my HIV (Human Immunodeficiency Virus) status comes positive? Please help.