lactose intolerant

So I think I am lactose intolerant. I am not completely sure, I haven't been to a doctor to be checked out. But people that I have know that are lactose intolerant have been knowing for years since they were kids. Is being lactose intolerant something you are born with or can people develope it over time? Bc anything dairy related upsets my stomach. I had a piece of cheese today and now i am currently on the toilet as i write this 🙄🤕