Can someone ples help me out here?

When you go into the doctor and they tell you to pee in a cup, when they run tests, when they look at the pee, would they be able to know if there's an std init without even running a test. I went to the docs and I didn't tell him that iv been sexual, but he ran a test. They say my test came up fine, would they still test the pee for any std even if you didn't tell them you've been active, I have no real signs of gunnaria or hurps or clap, I have no white yellow or greenish discarge havnt at all, all it is that now my balls just pretty much hurt, and rarly stings when I pee.... helppp