This certainly is a tough question.
SHY?
Women are taught to be discrete about their love, and often pine for their true love while they lose him. Women are taught to be shy, and never be forward. I don't think that women should be that way. Women must let people know how they feel so that can get what they want.
SCARING AWAY MEN?
Ordinarily, my advice is to be honest and open at all times, but I think that it is important to be a bit cautious about taking away man's role of initiating deeper relationships.
If he does not want to commit to marriage, or if he feels that he might accidentally hurt you by leading you on to a relation that is deeper than he intended, expressions of love might scare him away.
WRITTEN VS. VERBAL EXPRESSION OF LOVE:
Shy people can write instead of talk.
THE WORDS OF LOVE:
It seems to me that people fall in love without even realizing it (sometimes it is hard to pin down the exact moment that you fell in love with someone).
In general, women are more verbal about relationships, and men are more stimulated by visual stimuli.
Maybe actions describe your emotions better than words? You don't really need to be the first person to verbally express love.
Eventually, you will absolutely know that he loves you (or does not). At that point, telling him that you love him is advisable. Until then, there is no need to verbally express your feelings (though you can express your feelings in other ways (not necessarily sexual ways)).