First 5 Gallon Batch All over carbonated

I did my first 5 gallon batch with the Dark Cherry Stout Extract Kit w/ Specialty Grains. I bought the Siphonless Big Mouth Bubbler® - Ported 6.5 Gallon Plastic Fermentor to make it easier to bottle. I got it all into the fermentor put it in a closet with a steady temperature and let it sit for 2-3 weeks. I cleaned all my bottles right before bottling. I let them sit some in the fridge some not for 1-2 weeks. I used the fizz drops in each one. The problem I am running into is each bottle is overcarbonated. If I open a bottle like normal it all foams up instantly and overflows. Trying to figure out what I did wrong before I begin my next batch. Thoughts or suggestions are appreciated.

I can think of at least four possible causes for the over carbonation.
Fermentation was not complete when you bottled.
The bottles were not cleaned well and then sanitized before filling. Bottles you opened were infected.
Bottles were not chilled for a few days before opening.
To many fizz drops for the size of the bottle.

Give us some more details on the beer and sanitation. Was the specific gravity of the beer stable over a few days indicating final gravity had been reached? What was the Final Gravity?

How do you clean and sanitize your bottles? What is your cleaner and sanitizer?

What is the volume of your bottles? How many and what size fizz drops did you use.

Answers to these questions will help solve your problem. It may turn out to be as simple as chill time before opening. Any problem has a solution.