Hi, I'd like to help you with your question.
There is nothing wrong with being this man's friend. It sounds like you feel very strongly about contact with him. And that is ok as long as you feel it does come to the point you feel obsessed with him all of the time.
If you feel you are obsessed, then you may want to consider therapy. Obsessions usually indicate that there is something going on in you that needs addressed. In many cases, obsessions are based in unmet needs from childhood, usually deep seated insecurities. You want contact with that person because you need what you feel they have. It creates a kind of dependency on that person to fulfill your needs.
Therapy can help you find out what need that you have that was not fulfilled and help you find a way to deal with your needs yourself. To find a therapist, talk to your doctor about a referral. Or you can search on line at http://www.findatherapist.com.au/.
Also, learn more about obsessions through self help. Here are some resources for you.
Addiction to Love: Overcoming Obsession and Dependency in Relationships by Susan Peabody
How to Break Your Addiction to a Person by Howard Marvin Halpern
Confusing Love with Obsession: When Being in Love Means Being in Control by John D. Moore
You can find these books on Amazon.com or your local library may have them for you.
I hope this has helped you,