Given the data you provided (stopped using birth control pills at the end of june, having menstrual periods at the beginning of july and at the end of july, having intercourse on 26 august), the intercourse on 26 august might make you pregnant.
It is common for women who stop taking birth control pills to have irregular menstrual cycles. Therefore, it cannot be determined for sure whether the sexual intercourse was in your fertile days or not. The spotting in august only confirms that your menstrual cycle is irregular. However, even in this condition ovulation and subsequent fertilization might occur.
Therefore you are advised to visit a gynecologist for a physical examination, hormonal laboratory tests, and an ultrasound scan that would most accurately determine whether you are pregnant or not.