Hello, Thank you for writing to HCM, Bleeding while having sex is normal so nothing to worry. And as i gone through your query as you said your girlfriend is virgin than its normal thing while having masturbation. It should like her hymen might be hurt and due to that bleeding occur. But nothing to worry there it should be stop automatically. But just take care of one thing that while even masturbation you should have to take care that you dont getting too much excited and not hurting her internal. That would help to getting out to your query. It should be happen even if pre cum in vagina amount should be less. So while you are going for masturbation or intercourse i would suggest you that go for foreplay and Oral sex first before you go for intercourse because it will help for pre cum and also you and your partner will have more pleasure than normal intercourse. Also You may use lubricant if it happens each time you had sex so that penis could enter easily. Or you should use different positions in which penis enters easily. it also gives you more satisfaction and even more sexual pleasure. Still you are facing the same issue i would like to suggest to concern a good doctor and check for issue they will suggest you better. Hope you will find it helpful. Thanks & Regards, Dr. Gaurav Prajapati