Hallow Dear,
In the private parts, there are two large lips and two small lips. If you separate these lips, there are two openings in the space there. The upper opening is for passing the urine while the lower opening is vaginal opening through which the menstrual discharge flows and through which sexual intercourse is performed.
In unmarried virgin girl, a delicate thin fibromuscular membrane is present at the opening of vagina. This is called as
Hymen. During first, or sometimes during first few intercourses, this hymen gets ruptured (defloration) resulting into some amount of bleeding. You should not be worried about this bleeding. Please do not resist while he is inserting penis in the vagina. To avoid discomfort, initial insertion of finger helps sometimes. In this era, many girls' hymen is already ruptured before first intercourse. This can happen due to vaginal
masturbation, sitting astride on bicycle, horse, etc., athletics, tree climbing, etc..
If you find difficulty in penile insertion into the vagina, please use some lubricant. Oil based lubricants are harmful to the woman's reproductory organs; use only water based lubricants. Vaginal jellies are good for this purpose.
Intercourse under vision will help you to sort out this problem.
I hope this helps you.
Dr. Nishikant Shrotri