One thing is for sure, you are having problems with the experience you had. You should seek out someone that you can talk to (a professional) to help you work through your thoughts and feelings about it.
Looking at pictures (of any sort) does not determine your sexual orientation. Whether a girl you are interested in is interested back does not determine your sexual orientation. You said that what happened with your cousin was experimentation. There are certain ages where that kind of experimentation is more common (probably around 3-6 years and 10-13 years old), mostly because in each age group, we discover more about our bodies and our sexual "pieces-parts", so to speak. Experimentation does not necessarily determine your sexual orientation. You said, yourself, that you are not sexually attracted to guys. If you were, THAT would be a sure fire sign that you're gay. But, since you're not - that's a really good hint that you're probably not gay. I'm assuming that you are, indeed, sexually attracted to girls - though I did notice you did not specifically mention it. Rejection from girls can be hard, but their opinions of you is not what determines your sexual orientation, either.
My assumption (and it could be very wrong, I know) is that you are basing your concerns on what you've heard other people say. Try to remember that teenagers see more black and white in issues - and if they can get a chance to insult someone to make themselves feel better, they will! If you see that others are making fun of kids for certain experiences or behaviors, it may be easier to worry that they will think the same of you. And well, they might - but that's why we all have secrets. :) But it doesn't matter what others think of you, you are what you are.
Basically, you need to learn about yourself. If you're that worried you may be gay, take it on as a challenge to find out - rather than worry about what the outcome may be. If the outcome is bad - deal with it then, but try not to stress too much about it now. All that said, I have a 16 year old daughter. She's never dated. Apparently, only the "creepy" guys make it known that they like her, so she chooses to stay dateless for now. She admires the beauty of many women (Selma Hayek, for an example). But she is as straight of a girl as I've ever seen. Sexual orientation is a lot bigger part of you than small experiences or getting the short end of the stick in dating. And try to remember that an "all or nothing" mindset will only make things harder on you - and get help with the feelings you have over the past. I wish you peace of mind and the best of luck in finding the answers you seek!
Well, firstly, being Gay isn't a "disorder" of an emotional/psych. kind. It is just a way of being born a little different than mainstream.
And there are many many people who settle as gay and yet may have had a heterosexual experience in their teens, and vice-versa.
Then there are those who are bisexual, who like both men and women. And it's not wrong or disturbed to be like that either.
I can't say for sure, but it seems you like women! Lots of people have had homosexual experiences in their youth, that have been a part of sexual curiosity, and not necessarily the way they truly are, sexually.
I love men, and have always done, but I had one brief homosexual experience myself when I was in my late teens! It didn't "go as deep" as the heterosexual ones, so that's how I could really tell where my orientation was. It was like something I did for curiosity or fun, and not really where I was at.
Maybe the same applies to you? Sounds a little like it...