You seem to have developed some kind of "girl phobia" no matter how strange this may sound. Your condition meets all the criteria of a classical phobia. Phobias are quite easy to treat. I treat patients with a successful, intensive method that leads to full recovery. The patient is confronted with the cause of his/her phobia. In your case, if there is no girl available, you can use your imagination.
The patient gets a strong attack of anxiety that abates. When the patient gets tired, the treatment is suspended and continues at the next meeting. The first time is the most difficult. After that it gets easier and easier. After a few sessions the patient is released from the phobia.
It is difficult to treat phobias on your own. The anxiety is so strong that you do not dare to continue. Try to find a psychotherapist who is capable of treating phobias.