Bit of a query about this one, it's my first kit I've brewed, it was in the FV for about 2 weeks with a slight temp variation but nothing too much, it's been sat in the PB now for about 12 days the last few of which have been in the garage where it's been pretty cold overnight, I tried 1/2 a pint tonight and it was definitely drinkable but didn't have much of a head and wasn't that carbonated, I was just wondering if I were to use some CO2 on it would that change that? Thanks for any advice in advance.