I would like to perform STD testing to see I'm ok

Hello, my name is Olivia, I'm 18 and I think I have one of sexual transmitted diseases, but I'm not sure. I just have pains in my vagina. I had a few one night stands, and cause I would worry about my health I stopped having sex with strangers, and started a relationship with one boy. I wasn't aware whether he had infection, and I never asked him. At this time as I have the pain, I believe he might be. I would like to to check myself for any infection, but I'm so scared. I've heard about anonymous std testing, but I've never done it. I really would like to become well like everybody that's why I would like to do this examination. Can you please tell me how I can do it, so my parents will not see I did it. And do you know how much will it cost?