The question sounds something like I am comfortable being bi-curious, but I am not quite OK being gay. So, before I answer your question, you need to know what actually bi-curiosity is. Being bi-curious does not essentially mean that you are a gay or bisexual person, but, of course, you have somehow developed sexual interest towards members of both sexes. A bi-curious individual may identify himself/herself as either a heterosexual or a homosexual. Still, he/she can often fantasize about someone from the same sex (in case if, he/she is straight). On the other way, if the person concerned is gay, he/she may get sexually attracted towards a member of the opposite sex.
Sexuality of human being cannot be described in just one word, since it is not an either/or situation. Some individuals are, of course, 100% straight. They just dont feel any sort of sexual attraction towards the members of their own sex on any occasions in their lives. Again, there are some men and women who identify themselves as totally homosexual individuals. Sexual feelings towards persons from the opposite sex never arise in their minds. But, the rest of people, who form the majority section, hover somewhere in between. Some of them may describe themselves as bisexuals, some may be not at all sure about their sexuality (that means they are still questioning themselves regarding their sexual orientation), while the rest of them often or occasionally get turned on by persons from both the sexes, but is not yet ready to attach the bi-sexual label. They can be hailed as bi-curious. It is not necessary that a bi-curious person will have sexual encounters with members of their own sex as well as opposite sex. But, they will surely daydream about getting physical with a person with whom they are not supposed to have sex with.
Lets imagine the situation: Your friend appears to be very much straight and he even has a steady girlfriend. Now, you have suddenly caught him gazing at nude photos of other men in his PC. When you ask him about the issue, he admits that he often gets sexual pleasure looking at young, handsome men, though he never had sex with any man in his life. Here, you can hail your friends sexuality as bi-curiosity. Again, the situation can be something different: Your cousin calls her lesbian and she is quite sure that she wants to spend the rest of her life with the woman of her dreams. But, here too, one fine morning, you find her in a compromising position with her male friend. Being questioned, she frankly replies that though she is well aware of her sexual preference, she was just trying to experience how does it feel to get into the act with a man. These are just instances of bi-curious human nature. There may be thousands of other examples that suggest bi-curiosity among individuals.
As there is still some stigma attached to the terms gay, lesbian or even bisexual, most people tend to call themselves bi-curious. The perspective of bi-curiosity differs from person to person. For some, it is a provision of breaking free from conventional sexual monotony while for others; it is a way of keeping the options open. Being bi-curious surely makes you partly gay, because you cannot escape the fact that you have both homosexual and heterosexual tendencies. Again, you are not totally gay, because though you may have got into sexual relationships with men only, deep inside you preserve a curiosity of exploring the female anatomy too. But, whether you are gay, bi-sexual or bi-curious, you are an absolutely normal human being. Theres nothing wrong in felling the urge of having sex with both men and women, so be comfortable with yourself and your own feelings.
There are lots of men who identify themselves as straight, yet they have no qualms about having sex with other men. They just cannot resist themselves of obtaining the pleasure of having sex, be it with a woman or a man. Sometimes, admiration for a person from the same gender leads to sexual attraction. These sorts of crushes are more common among the girls. But, whatever it may be, each and every person should express his or her sexual desire freely. Getting curious about another persons body is neither unnatural, nor offensive.
May be the terms infidelity, unfaithful are more associated with being bisexual, but a person cannot always have control over his/her feelings and emotions. What if they feel indomitable passion inside their hearts for people of both sexes at the same time? It is not at all healthy to keep all desires suppressed. It can have negative consequences in future. So, instead of bothering over the issue of being gay or being bisexual, you must do what you feel like. Get over with all your fears and apprehensions and ask your inner self about your exact orientation, because, you will be the best person to judge your true nature.