Well, you are born on the cusp of Sagittarius and Capricorn, so you might have traits from both signs within. Strict Capricorn would certainly help controld those wild Sagittarian urges. But Sags do have a lot of fire though, and when we get passionate about something (whether passionately angry or passionately happy - what have you) it can be hard to hold it in. Our blundness can truly hurt! It's not that we mean to. It's just our nature. And I've occasionally gotten the impression that Taureans aren't always as thick skinned as they would have us believe...

However, you didn't mention any other planets, such as Moon, Venus, Mars, Saturn, Pluto or house placements in yours and your boyfriends' chart. Knowing this would make it more obvious why things turn out the way they do.