I see myself as a Buddhist and I would like to take refuge. Can I do it alone ? Will I be considered a real Buddhist ? Please excuse my mistakes, English is not my first language.
Yes you can take refuge in the triple gem (the Buddha, the Dhamma, the Sangha) alone.
Here are 2 links for you.
The second link describes how to take the five precepts. They are normally taken after taking refuge in the triple gem.
May you be well and happy and free from mental and physical suffering.
You mean taking the three refuges in the Buddha, the Dhamma and the Sangha (http://en.wikipedia.org/wiki/Refuge_%28Buddhism%29)?
Or do you mean taking the precepts (http://en.wikipedia.org/wiki/Five_Precepts)?
In any way, you can take them by yourself.
You need to clarify your motivations.
If you believe the teachings of Buddhism to be true, then you are a Buddhist when you practice Buddhism, and no ceremony in the world will change that.
On the other hand, if just want to label yourself as a Buddhist to others, then the ceremony (and any other paper-work) is the most important thing you can do.
One aspect of taking refuge is your commitment to develop the qualities of the triple gem in you.
Yes you can do it on your own without anyone else involved.
You don't need an external entity to call you Buddhist or declare that you are a Buddhist, it all depends on your cultivation and practice.
(Edited from the Wikipedia link to make it complete)
Having taken refuge in the Buddha a Buddhist should not go for refuge to other deities or teachers salvation and enlightenment. (You are making a commitment to practice the Buddha's path with faith that this reaches the final goal of enlightenment and salvation and setting aside other practice hoping that it will take you there so you are given fair trial to the technique. Setting aside other practices so you have faith in what practice gave you the results. ) You should understand and try to develop the qualities of the Buddha in you.
Having taken refuge in the Dharma a Buddhist should do no harm to other sentient beings. Also set aside other practices, teachings, rights and rituals aimed at achieving enlightenment. Also develop the qualities of the Dhamma in you.
Having taken refuge in the Sangha a Buddhist should not rely on heretics (teachers and practitioners of other forms of rights and rituals aimed at achieving enlightenment and salvation) as means to achieve enlightenment. Also develop the qualities of the Sangha in you.
What's the old adage, "We don't become Buddhist. We just realize we already were Buddhist".
Becoming Buddhist can be done alone by taking the 5 precepts and being earnest to follow the path; however, the path is hard. Thus, saying you're a Buddhist is really the easy part. Remaining on the Buddhist path is the hard part. At a minimum, you have to live compassionately and align your thoughts with your actions. That's pretty hard stuff and why the Buddha made the Sangha one of the three gems that help us with our practice.
The other reason Sangha is important is that Buddhism is less about knowledge (although that's there) and more about wisdom. Wisdom allows us to gently work in difficult situations and be truly compassionate while others are filled with passions. The wise application of what you know generally comes by interacting with a teacher and other people. Other followers can catch you when you fall and provide an ear when you feel weak. That's difficult to do alone.