Should I break up w/ my boyfriend because he sends text messages to his ex and...

...still calls her? My boyfriend works with his ex. He sends her text messages and calls her and he tells me that it's work related. His ex wants him back. She sends him text messages like "Goodnight" and calls him in the middle of the night to make me mad. My boyfriend and I have been together for a month but we are always together everyday. I'm not sure whether I should trust him or not.

Sounds like you're a rebound girl. Since it's only been a month and you're not fully invested in the relationship yet, take it easy and see where it goes. I'd say if it's still the same in a month or two, ditch him.