What Causes Indigestion And A Discolored Tongue?

recently ive been waking up and feeling very indegested.A couple of weeks ago i woke up feeling the same way, but didnt think anything of it. A few hgours later while i was at the gym, i spit into the garbage ,only to notice it was almost black in color. When i got to a mirror i looked at my tongue and noticved it was a dark brown, almost black in color and somewhat orangey yellow in other spots, it almost looked like tiger fur, and it had an almost hair like texture. since then everytime ive woken up with indegestion ive noticed my tongue being discolored, and oddly textured. Ive tried to relate this to foods but i havent eqten any foods of that color. Could this be an allergy to something? or maybe a defficiency? Its starting to get me worried that it could be symptoms of something much worse.