How can I remove my desire for a relationship/girlfriend?
What helped me tremendously distance myself is this:
Contemplate the various advantages and disadvantages of having a girlfriend--particularly the one that you think you would get--not the dream-woman-that-you-have-to-be-on-a-certain-level-you-are-not-at-to-get. 

For example, here is a personal list of benefits of celibacy:


Jing retention for transmutation into spiritual energy (chi, shen)
Time saved for spiritual and personal goals.
Money saved for spiritual and personal goals and fun.
Mental energy saved from all the headache and back and forth.
Social energy that can go into practical things like helping people or myself rather than feeding a woman's ego.
Less stress for managing a relationship... peace
Less stress about her cheating on me every day... peace


And disadvantages:


Lack of endorphins and excitement
Tactile loneliness
Social ignorance
Sexual ignorance
Intellectual ignorance about X


At this point you should have an overall idea if there is more advantage or disadvantage.

The last step is to FIND activities which address the disadvantages.


exercise
joining a sangha and doing social activities together
learning more more about female evolutionary psychology via videos/books (see Red Queen, Sperm Wars)
getting actual results of Buddha dharma


Lastly, I would say that it is best to pursue your path and not look for anything external because that external (i.e. girlfriend) when it comes to you "naturally" will be extremely well-matched for you (a great companion on your spiritual journey). Maybe it's because you started teaching or you were really successful and someone who values it took notice, etc.... let her find you.

Pursuing an un-ideal relationship would take you off the market and you might miss that girl of your dreams BECAUSE you were looking for her consciously and/or are with someone! Strange, isn't it? The best thing may be to be celibate until hotly pursued by someone well-matched. If it doesn't happen and you put all your 100% effort into the benefits list... then not much is lost!
But had you done the opposite... you will regret the sexual life for maybe eons or however long you think until you are a human and above with Buddhadharma.