It sounds like it's about illicit, probably gay, sex. I have read that the first 120 sonnets were addressed to a fair youth and the other 20 odd to a dark lady. I would have to take that on trust. IIRC, the more romantic or risque poems in the first 120 poems do not mention the gender of the subject. However the subject of other sonnets in the sequence is male. In some of the early ones, Shakespeare recommends his friend to father some children in order to reproduce himself, which sounds both gay and not gay.