I hate these text!!

So my boyfriend and I have been dating for 9 months now, so I can tell when he is mad or upset with me. Whenever I get any text messages with " yup!, k, or yea" I know something is up. When I get those I Ask if everything is okay. Well it annoys me when he responds with yup! I have told him many times before that whenever I get those messages I worry because it means there is something wrong. He has told me that at times there isn't anything wrong. So my big question is how do I deal with someone who texted me like that and I'm here worried that I did something wrong?!? Does anyone else have this issue?