I am going to put an asterisk on everything I am about to say.
1.100 is a little high. I generally aim for about 1.090 and that will give me a potential alcohol by volume of about 12 percent ( 090 * 131 = 11.8) . 1.100 will give you a potential ABV (alcohol by volume ) of about 13 percent. So nothing to frighten the horses. Your yeast will handle that ABV with few problems.
Here's the reason for the asterisk: You are making a must from bananas. Bananas are very rich in carbs and those may be providing a significant portion of the reading you are taking from the must. How thick is the must? Did you add any of the goop from the bananas to your fermenting bucket or did you keep the fruit in a bag which you have now removed and so are measuring more or less the sugar content of the must? How much additional sugar did you add per liter.
A typical banana is said to contain about 17 gms of sugar = .6 oz. So that means 40 - seven inch bananas will provide enough sugar to raise 1 US gallon of water to a specific gravity of about 0.040. So will 1 lb of sugar. So if you know your volume (you say 12 gallons ) and you know how many bananas you added and how much sugar you added then you can calculate the probable gravity that comes from the fermentable sugars. If that is close to 1.100 then you are in the ballpark you think you are - and in my opinion , that ball park is reasonable. If the gravity by calculation puts you in a very different ball park suggesting much more sugar than your 1.100 reading or if the calculation results in a number much below 1.100 (so you don't have anything like 12 percent ABV then you may want to take stock of your recipe and your wine making technique.
