I see several red flags. First, You can't blame your girl friend - the responsibility for how you treat your body lies with you and only you.
Next you say you're not concerned with muscle. This is a mistake and lies at the root of the diet yo-yo. You really want to work on gaining or, at least, maintaining muscle when losing fat. It all works much better that way.
Finally and, perhaps, most importantly - you need to change your attitude about fitness. Diet and exercise aren't just something you do to GET fit, they're what you do to BE fit. If it's not a permanent lifestyle change then the results will be temporary. The need for immediate results probably isn't keeping you from committing. If you are like most people in your position you don't really believe that fitness is possible for you. It is.
This reply may have seemed harsh. Sorry. Try to read the honest concern between the lines.
Start slow, read a lot, get your diet under control, build a sound
exercise plan, find some role models you can look to. You'll see results.