When your young, you have opportunities: you may not realize it now, but it is an advantage that you're young. There's no rush to decide what you want to do for a living, where you eventually want to lay down roots and live, or even who you want to be attracted to and marry. Those things take time. Some people decide late in life that they want to go back to school to pursue a certain career. Others, somehow, know almost from early teens that they love a certain subject and what they want to be when they start work.
The advantage of being young, is that you seriously, have your whole life to make such important decisions. At 18, maybe you're not sexually active yet. But, in time, you will have opportunities to be with people you find attractive. Don't put pressure on yourself to start experimenting until you are ready. And the ultimate choice, of whether you are gay, bi, or straight does not have to be made today, tomorrow or next year. There is no date that such a choice becomes required. Myself, I didn't lose my virginity until I was nearly 21, believe me it wasn't for lack of trying though! The key is, there are other things you can do with someone..it doesn't have to be "sex" and it doesn't have to be penetration (whether gay or straight).