Hi, You cannot be pregnant at all. Intercourse during periods is usually considered safe unless you have very short cycles. Ovulation occurs two weeks prior to the onset of the next menstruation and this is the fertile period when you have to take precautions. Complete penetration or ejaculation is not necessary for conception to happen. Pre-ejaculate contains enough sperm to fertilize an ovum during the fertile period. Since you had a normal period after the incident, you need not worry. In future, to avoid undue stress, please use some form of regular contraception. Hope this helps.