Help! Our house help infected me

I am a Form One student and I think I have a sexually transmitted disease. I have had sex with our house girl. It was my first time, but she seemed as if she was used to it.

Urinating has become a problem because I feel so much pain that sometimes I cry in the toilet. I have also noticed some bumps with puss around my private parts and I don’t know what to do. I can’t tell my parents because they will kill me. What do I do?
{Jonnie}