Well,I used to give readings professionally but I am feeling tired and not in the mood to write anything long.
But I will say this, you Moon and him Saturn yours is an emotional connections but the reason he may dislike you is your too emotional of a woman for him- your emotional,sensitive, kind, nice, with feelings, dreamy-and he dislikes and-or doesnt understand those character traits- so if you wish him to like you more refrain from showing your sensitive side that often and-or learn how to be sensitive but at the same time sounding rational and calmer,stable. Not that you are not that, but just he prefers women who are less sensitive and womanly as you. He likes the more colder, earthly, practical types.
The other woman is Venus in Scorpio, and yes, it does look like he was with her and it does look like she was the sex kitten that night. However, both of them are in the sign of Scorpio ( neither are in the sings of the other,so there is no love and or desire between them,because Scorpio isnt directed towards either Saturn or Venus, but Mars ) which makes me think 2 of the following things
a ) Your guy is actually deeply and jealously so in love with a female friend of his ( Mars rules his 11th ) and was with another girl, Venus in scorpio, who is very jealous because your boyfriend loves the girl represented by Mars. So whomever Venus was she was jealous and very possesive and vindictive and jealous of Mars ( Venus in Mars'ses sign, detriment, feeling ill feelings because of Mars )
OR
B ) Your boyfriend had a one night stand or fling with a woman ( Venus ) who has a boyfriend ( Mars ) and she wanted to make him jealous so hence she slept or is sleeping with your boyfriend. Venus has no interest in Saturn, but Mars, and sleeping on the side whilst being in a relationship is something that would fit this Venus very well.
P.S. Oddly, you don't seem in love with him,just emotional about this issue for the sake of your own self.