This usually happens when a person is perceived as having lower value. In general, you should take the necessary steps and eliminate anyone who is not willing to pay the price required to deserve you, from your life. For a woman to perceive your value, you have to make her put some work into hanging out with you, for her to value your presence. You can do this by making her do favors for you, such as picking you up at home or paying for your dinner. By doing favors for you, she will convince herself that it must be with good reason and that you must be a nice person, which explains why she cares for you.
People place more value into things that require more work and effort to achieve.
By not always being around your girlfriend, you will be perceived as scarce and hence, more valuable. In fact, you should be willing to withdraw your time and attention from her from time to time. Once in a while, cancel dates and don't always return her phone calls. Men that do not stand up for themselves lower their value because women perceive them as free rides. For example, let her know politely that women who try to play head games with you are kindly escorted out of your life without hesitation.