Welcome to HealthcareMagic
If information given by you about your periods and sexual acts is correct and your periods are regular then u have rare chance of pregnancy
. If u had sex on above said dates only then those were safe days. Have u confirmed your pregnancy by urine preg test?if no then do confirm before taking any medications. For urinary infection u can take antibiotics. It would be better if u consult your gynecologist.Take care.