Im a straight girl, but I can still look at the female form and find it visually appealing. It can be beautiful, worth drawing and gazing at for a long time, but I never ever find it a sexual thing. Its beautiful the way a work of art can be.
I think if you are getting sexually aroused by men then there's a good chance that for now at least you are bisexual, if only midly so. Im a believer that sexuality isnt a static and unchanging thing, its always redefining itself. You might be bi-curious, newly bi, or have been bi for a while and just denying it. It must be a confusing time at first, but if you remember that everyone is different, and dont try and label yourself too strictly, you should be free to explore how you feel. In the same way that we date different people to find the right one, you might be experimenting with both genders, before you decide who you are attracted to, one, both, or neither.
As for what you can "do"... if you want some help from professionals google tells me the London Lesbian and Gay Switchboard Tel: 020 7837 7324 is good. also the samaritans 08457 909090 can help you if you are feeling down, and should be able to provide you with plenty of infortmation and advice.