A compulsive gambler always loses, because we cannot stop gambling. A compulsive gambler is usually also a compulsive liar because of the shame we feel when we are caught in our addiction.
You NEED to stop gambling – put barriers in the way of gambling, bar yourself from establishments or use a blocker for gambling sites. As your girlfriend knows you have a problem, involve her in your recovery. Get her to handle your finances – just giving you a small allowance to get by on. You need support locally through GA or similar in your country or if you can get counselling.
Finally try and focus on something else you enjoy that does not involve gambling in any way. That will mean you making new habits – instead of betting when you are at a loose end.
I wish you well.