Percy, welcome to SR. There are lots of wise individuals here and if you do decide to quit and need support, you'll find it here.
Some people will say only you can decide whether you have a problem with alcohol or not. They say that there are a few warning signs though, and these include regularly drinking by ourselves, often struggling to stop once we start and causing people to get concerned over our drinking habits (which your girlfriend seems to be, if I understood you right).
It is also a progressive condition that leads to increased consumption over time, and sometimes even over a relatively short period.
Stick around, read and post. I am sure you'll find useful information to help you decide what is right for you.