Is there magic that prevents pregnancy, and is there something greater than magic, as the Sheikh mentioned?

Sorcery can be a cause of infertility or miscarriage. It is not advisable to go to the man mentioned, as his words indicate that he is one of the soothsayers, and going to them is forbidden by Islamic law. The spouses should perform Ruqyah (Islamic exorcism). If the man intended that there is something stronger than sorcery, he perhaps meant envy, although there is no religious evidence that the effect of envy is stronger than sorcery.