Hello Saratem,
This may be too foward for "some people", but make sure you have some foreplay before. Also, you can buy a vaginal lubricant at the pharmacy to use on your nether regions before intercourse. The more physical pleasure YOU have before intercourse, the more likely he will be able to go inside. Finally, relax your muscles before penetration. When nervous, women tend to contract their muscles and this makes it harder. Of course, see a doctor it persists. PM me if you want more details, as many ppl here seem to be repulsed by what is a natural part of life