Yes he did in School Hard. However Spike lies a lot and he may have just been boasting. Alternatively maybe now that he has the hots for Buffy he wants to spare her that detail. The Angel story 'Damage' also deals with this question
p.s. She could have because she had a son. Lie? Spike does half truths and or could choose to remember how it suits whatever he is telling and to whom he is telling said story(ies)