Your husband texting his boss?

Ok so how would you feel if your SO texts his "Boss" at all hours? Sometimes he just randomly smiles and laughs at his phone regardless if we are at home eating dinner or out as a family. Every time his phone gets a text I ask who it is and it's always her! 😡 I tried not to get bothered but it's starting to piss me off. When I confront him he always gets defensive and says she's my boss or its work related. I've gained tons of weight after having our 2nd baby so of course it makes me feel even more insecure that he's texting "his boss".