Why did I display homophobic behavior as a child when I am gay myself?

I have only recently acknowledged to myself that I'm a lesbian. This however got me thinking about how up until about 4th or 5th grade, my friends and I would use "gay" as an insult to kids we didn't like. We knew exactly what it meant but did it anyway. I didn't have problems with actual gay people (my sister's friend was gay and I never thought negatively about him at all, etc.). Then some time around middle school I became very pro gay rights and anti-bullying and have been that way ever since. So despite not actually having an issue with homosexuality and being gay myself (without realizing it), why did I partake in homophobic behavior when I was younger? Has anybody else had any similar experiences? This issue is making the whole thing more stressful and confusing. I feel extremely guilty for essentially betraying myself and the LGBT community. I'm trying to make sense of my behavior so I can move past it for good.