Hello Doctor, I Have Itching In Groin,under Arms And Near

Hello Doctor,
I have itching in groin,under arms and near buttocks and i can see patches in these areas.I am skeptical if this is normal skin infection or any STI.I have had safe sex before and have used condoms properly.But still i want to have screening test once for STD/STI to get my doubts cleared.Could you please tell me the centers in Bangalore where i can get the tests done along with approx cost.Do i have to specify individual tests for STI in these centers or if i just say Screening test will it be sufficient.Please advise.