Often, a person's sexual orientation cannot be discerned by looking at their clothes or even the way they talk. It's important to remember that words, gestures, and actions have multiple meanings. For instance, "gay" has had a sexual connotation since the 17th century. However, it originally meant bright, merry and showy. Some people still use the word this way to describe things like a party or dinner.
If your boyfriend seems to be fixated on men and doesn't mention it, he may be gay or interested in males. It's likely he doesn't want to come out because of the prejudice that is associated with homosexuality and because coming out could affect his career, family life and other aspects of his life.
Your boyfriend might lash out at anyone who mentions that he is gay or shows interest in males. He might say he is straight, despite the fact that he has a lot of love for gay people and a desire to see society become more accepting of them.
You might catch him glancing at another man in the street or in a public place. Or you might notice him engaging in suspicious nonverbal behavior with a man -- for example, a lingering gaze or a hug that feels too long. These are hints that he is gay or interested in males, and they should not be ignored. Having an open and honest conversation with him about his interests and yours might help him find the courage to be open about his sexual orientation.