I lie to my girlfriend of two months frequently
Why would you go ahead and lie to your girlfriend on purpose?
Because I like to.
You shouldn't lie to your girlfriend frequently it is bad to lie to her. Instead of lying to her you should be honest with her to build trust.
I'm honest with her, but all honesty leads to is doubt.
I don't think that is true. It's bad to lie to your significant other. Honesty is the basis of all relationships and you should do what you can to be honest all the time.