I don't have children so I don't think I should express an opinion. I haven't slept with a parent since I was 8, and that was on vacation.

Does your male housemate have any rights in this situation, though? (Is he your son's father?). You don't have to tell us, but if he does have a right to be involved, it's not up to your therapist or us whether this is OK, but the two of you. If he has no rights - a roommate or more distant relative - then it's your decision.