While there is no proper 'diagnosis' that can tell you that you are lactose intolerant, but given how common it is, if you face problems such as indigestion, gas, flatulence, and excessive burping every time you consume dairy (or frequently after consuming dairy products), you are probably lactose intolerant. However, if you believe this is something that is affecting your daily life in an adverse manner, it is best to get in touch with a doctor and to get yourself checked for it.