How did you swallow a condom? Was it at least flavored?

No, swallowing a condom will not mutate your semen and can in no way prevent you from impregnating a woman. It may, however, seriously affect your digestive tract so you may want to contact your doctor just in case. You really don't want to have an intestinal obstruction.

By the way, what is it that you do for a living that can't be revealed to your girlfriend?