Why Does Beer Mess Me Up?

Ever since a few months ago if I drink more than 2 beers I get a terrible headache. This is recent it hasn’t always been like this. On the other hand, i can drink at least 6 shots of bourbon 113 proof (The Representative) and not be hungover(I do feel Groggy though). Somebody told me I may be allergic to beer. Also the beers are usually Coors, Modelo, or Stella. What’s going on with me?