Northern Brewer Fizz Drops Question

I just tasted my second Northern Brewer Irish Red Ale and both were very fizzy. This was a one gallon kit which included NB's Fizz Drops which I had not used previously and the beer has no head but is almost as fizzy as a soda, anyone have this issue or know what is wrong? The beer has been in bottles for over a month and the one I just drank was in the fridge for a week. Not sure if the drops are too blame or if something else is wrong. Any suggestions or comments would be appreciated. It tastes fine so I don't think it has anything to do with an infection.