Hello. Thanks for writing to us at healthcaremagic This condition in which just a slight stroking of the skin causes it to become red is known as Dermographism, a type of physical urticaria. It is chronic and treatment is mainly symptomatic. Dermographism is entirely a different condition and is not suggestive of an STD. Since your last sexual activity may not have been a completely protected one because of condom slippage, therefore it counts as a risky exposure. Screening test for HIV which was negative at more then 4 months after the contact is conclusive and you don t need any further testing for HIV. However, you may undergo testing for other STD s like Herpes, Syphilis (VDRL) at a center of your own choice in your region. These tests are available with most labs. For dermographism, I would suggest an OTC oral antihistamine e.g cetrizine 10 mg once daily for symptomatic relief from itching. Regards