1) Relax.
2) Become aroused. Foreplay and making out more can help.
3) Use lubrication - water based.
You are either not lubricated, aroused, or relaxed enough and causing damage. Whether it is your first or 41st time, you should never experience pain or bleeding.
It very well could be your cherry popping slowly
May I suggest that you go to medical professionals ( health clinic or hospial non-emergency) to be evaluated for a possible Friable cervix. Turn your worry into answers!!
It happens because you're probably not fully relaxed and your tense so it's a lot of force on your hymen, it could also be because you're stretching your hymen causing it to tear and bleed but it only happens after your first time and then possibly the next few times. If it still keeps happening you should talk to your doctor about it