You are doing it without a condom and it starts burning?

If you mean penile penetration into the vagina or anus without a condom and your penis starts to burn, it is possible your partner has a vaginal infection OR the E Coli in the rectum is irritating your skin. If a woman has vaginal yeast infection, she will have a white clumpy discharge. If greenish, it is a trichomonis infection ("trich" pronounced like "trick" but spelled with an h). A female's fluid should be mostly clear, "like" water. E Coli can cause urinary infections in males or females. It is important to wear a condom to prevent pregnancy (vaginal sex) and prevent diseases and infection (vaginal or anal). When burning begins, stop, go wash with warm soapy water including the scotum, dry off and put on a condom.