First of all, your girlfriend is likely to be very careful about sex, even very resistant to sex, because boys and girls have very different ways of thinking. Boys think that love is sleeping with girls, but girls think that love is actually suitable for boyfriends to eat and chat, so your girlfriend may not even think about sleeping. Of course, you chose such a sudden refusal, but after a while, you will get closer and the problem will be solved.
Second, it may take your girlfriend some time to examine your personality slowly, because many men really wear masks in love. Without careful investigation, it is impossible to see whether such a man really loves this girl or just wants to play with her. Some love rat will choose to break up with her after sleeping with her too much, and finally abandon her mercilessly. So it is very likely that your girlfriend needs a period of time to develop slowly with you, and then she can rest assured to slap you after seeing you clearly. Please don't lose heart and fall in love with your girl because of one rejection.