I think tastes change just like with anything, if your not comfortable with yourself liking guys then maybe you don't like them that much, Once you start satisfying your attraction to girls then the other side may handle itself.
You might think that having an attraction to guys is wrong which makes you feel dirty but you should learn to love every side of yourself, it's just part of growing up.
I'm a similar age to you and in a similar position, I'm just going with the flow, I'm a virgin and the thought of being in a relationship really scares me. There's part of me that doesn't want to date someone but I try to push myself out of my comfort zone or else life would just being boring.
The hardest part is not knowing what to do about my attraction to guys, I fancy good looking and fun guys but I really don't think it's sexual, I'm way more comfortable with girls, I would go as far as saying I'm inherently homophobic, I struggle with male contact, I'm starting to think that if I made more effort with male relationships then my interest in them would be satisfied by that friendship. Your not alone in being insecure, things like this sort themselves out over time, there's no one forcing you to do anything, just learn to relax because you're not doing anything wrong either way.
Actually.. im doing as for me..
how can.. i enjoy sex.. with guy.. if i have feeling of something dirty and bad, wrong...