The short and easy answer is, no: enjoying looking at breasts or lesbian erotica does not mean you are a lesbian. Someone is a lesbian if she calls herself a lesbian, and usually that means she is primarily attracted sexually, romantically and emotionally to women and rarely if ever attracted to men.
In fact, many other self-identified heterosexual women enjoy looking at other women’s bodies. I once heard a woman refer to herself jokingly as a “boob-isexual.” She has always been attracted romantically, emotionally and sexually to men. She finds breasts arousing and attractive but has never wanted to be in a sexual or romantic relationship with a woman.
Most sexologists and psychologists agree that few people are exclusively heterosexual or homosexual. Most people, they say, fall somewhere on a continuum between gay and straight, and most people’s “sexual orientation” is fluid (changeable) over a lifetime. We humans are marvelously complex, and simple labels like “straight” and “gay” don’t account for our infinite diversity.
Alfred Kinsey is one scientist whose research suggested that people do not typically fall into the neat and easy categories of “heterosexual” and “homosexual.” He developed a scale from 0 (exclusively heterosexual) to 6 (exclusively homosexual) with which to describe one’s sexual orientation. You can read more about the “Kinsey Scale” online.
Similarly, many people don’t think of attraction as a simple “either/or”: “I am either attracted to someone or I am not.” Instead they think of the many different ways they might be attracted to someone—whether for going on a hike, looking at someone, having a conversation, having non-genital sex, having genital sex, having children, or sharing a home. By asking themselves “the ways in which” they are attracted to someone instead of “whether or not” they are attracted to someone, they find they are “attracted” to many people in different ways and for different types of activities: some sexual, others not.
Using an expanded idea about what it means to be attracted to someone, it sounds like you may be “attracted to” looking at breasts and watching girls having sex with each other, but not attracted to having sex with girls yourself–a perfectly valid set of interests.
–Amy Stapleford, M.Ed.