If you're afraid of rejection, you may be acting too tentatively. Here's a simple rule to follow. If you persist for one moment beyond that, it's sexual harrassment or worse. There's always a next time. And in the meantime, perhaps you should review your romancing style.
Courtship rituals take place in every species.
There are moves the male makes, moves the female makes. In our species and in our society, the man makes the moves by taking the woman out, wining and dining her, giving her gifts, perhaps, but certainly lots of time and attention. He is then expected to be the aggressor sexually. Follow the ritual, even if you think it's bullshit. Love her for her mind and her good qualities.