Hello.  I am a highly educated mid-twenties male who is having trouble
rationalizing recent events pertaining to sexual identity. I am in a
committed relationship with an absolute dream woman who I plan on
marrying.  Over the last few years I've had recurring fantasies about
being sexually intimate with men or with a woman and man at the same
time. These fantasies are of the nameless, faceless variety that focus
on phallic fixation above all.  I've even found that  my occasional
web-porn jaunts lead me to bi or gay websites that I find arousing.
Until recently I've written these thoughts off as curiosity and
nothing more.  But the frecuency of occurrence has increased, and I'm
finding it more difficult to disregard these fantasies as meaningless
and have actually thought of "trying it".  I do know that I have never
been sexually attracted to a man.  At the gym I'm always stealing
glances of the women and never the men.  This is confusing me.  Am I
bisexual for wanting to carry out these fantasies? Can I maintain a
healthy relationship with this woman without ever satiating my other
sexual desires?

Thanks in advance.

Q1.)Am I bisexual for wanting to carry out these fantasies?
 
That's up to you to decide; nobody can make that decision for you, and
nobody has the right to tell you your decision is wrong. Bisexuality
isn't about WHOM you sleep with, it's about HOW you feel; so a good
rule of thumb in defining your sexual identity is not what you've
done, but what you'd like to do.
It is natural for people who are coming to terms with a sexuality
which is not society's norm to be feel confused.
 
 A strict definition of a bisexual would be someone who has romantic
and/or sexual relations with other people of more than one sex (though
not necessarily at the same time However, since not everyone has
necessarily had the opportunity to act on their sexual/romantic
attractions, some people prefer a looser definition; for instance,
that a bisexual is a person who - in their own estimation - feels
potentially able to have such attraction. This could be anyone who has
erotic, affectionate, or romantic feelings for, fantasies of, and/or
experiences with both men and women. (From Bisexual FaQ The Alliance -
Michigan State University
http://www.msu.edu/user/alliance/faq/faqbisexuality )
A bisexual may be more attracted to one sex than the other, attracted
equally to both, or find people's sex unimportant and strength of
their attractions to men and women may vary over time.

Q2.)Can I maintain a healthy relationship with this woman without ever
satiating my other sexual desires?

Ultimately, the decision is yours, and must be made by you. It depends
on the individual. It's like asking "Can a straight person be
monogamous?" Some bisexuals are monogamous, and some aren't.
 
Bisexuals are as capable as anyone of making a long-term monogamous
commitment to a partner they love. It is useful to distinguish
bisexual identity and bisexual behaviour. People who call themselves
bisexual are saying that they are attracted to both men and women.
They don't necessarily have to act on that attraction.
 
A bisexual deciding to be monogamous is not deciding to be "gay" or
"straight." They are still bisexual; they have chosen a person to live
thier life with, not an orientation, preference or idealogue. It is
important to recognize that they still feel bisexual.

Here are several links to understanding Bisexuality.

An Introduction to Bisexuality
BiNet BC  
http://binetbc.bi.org/primer.html

Bisexual Resource Center
Pamphlets (available online)
http://www.biresource.org/publications.html
I Think I Might Be Bi (now what do I do?)
How do I know if I'm bisexual?
http://www.biresource.org/pamphlets/mightbebi.html

Bisexuality
Bisexual Identity
http://www.biresource.org/pamphlets/bisexuality.html

Bi The Way
Myths and Truths
http://bitheway.org/Bi/Myths.htm

Bisexual FaQ 
The Alliance - Michigan State University
http://www.msu.edu/user/alliance/faq/faqbisexuality

Search Terms
Bisexuality
Bisexuals monogamy
Bisexual Resources
Counseling for Bisexuals

Thank you for the quick, concise answer and the informative links.