I read this one fic ages ago and I cannot find it but it was young alpha D who had never been with an omega in heat and omega G had never had a good experience with alphas in heat/ had never gotten knotted before but he had a problem with his heat suppressions so his heats always hurt but G needed someone to spend his heat with and D volunteered, saying he could learn how to take care of an omega but the first wave of heat when G needed a knot D came immediately and G was left sad and sore with no orgasm but D is such a good alpha so he learned and G had the best heat of his life after that and learned how good knots feel!!!!!