I don't quite get that he's seeing someone else, but it does look to me like your relationship is likely to end, regardless. If you really love him, I am sorry about this.
Venus (you) applies to a nice trine with Mars, but before it can perfect, Mars slips into the next sign of Aquarius. The moon's next aspect is a square to Jupiter, vs. a nice aspect to Mars.
Of course, if you have direct evidence of someone else in his life, then I would be mistaken. But right now it looks like he just wants to distance himself. Mars has been under a lot of stress lately. He may just want to be more on his own.