Welcome to the Barking Bears, boneyfloopjack.
As others have pointed out, there are many more questions that must be answered than just your height and weight, in determining ski length.
Remember that on the World Cup slalom circuit, athletes far heavier, and presumably more powerful, than you are skiing on 155cm skis. 155cm is the shortest allowed on the Men's circuit. Otherwise, I suspect they would go even shorter.
191cm these days is a big ski, regardless of what type of ski it is. I'm 6'1", and though I only weigh about 150 pounds, I used to ski 204-210cm skis. Now the longest skis I own are 183cm, and the skis I usually ski on are 173. The shortest are 123cm--and they work great!
My best recommendation is to seek a good instructor and ask for recommendations based on your skiing skills, skiing preferences, and size.