I'm afraid to upset you, but still no, even purely theoretically, sperm will not be able to leak from the stomach into the egg. To begin with, the sperm in the stomach will be exposed to gastric enzymes and change their properties, losing the possibility of fertilization. And then, if with an acute stomach ulcer there is a possibility of the formation of a through defect in the stomach wall, then with erosion of the cervix, no perforation occurs. Thus, the sperm-traveler will not go anywhere from the abdominal cavity.
By the way, the very term "cervical erosion" is outdated, now it can be considered colloquial. The correct name is cervical ectopia.
The stomach is acidic, and sperm live and are active in alkaline. So, with the greatest desire, they won't even make a couple of steps out of the stomach, even if you cut a direct path for them to the fallopian tubes (where fertilization takes place).
Even if we assume the incredible that the girl will not die from a stomach perforation before she becomes pregnant, it is unlikely that the sperm will overcome the almost one meter path to the uterus (since not in a straight line, but skirting the tightly folded intestines) without dying along the way. From a blowjob you get pregnant only in fairy tales.