I wonder, would it help to think of understanding your sexual orientation and exploring your first romantic relationships as things that happen at the same time, rather than as things that have to happen in a specific order? You're at an age where one is likely to give you clues to the other. For instance, who you get a crush on my give you information about your orientation. Does that all make sense?
If you're looking for more general information on things that can help you work out your orientation, this article has a lot of useful advice: The Rainbow Connection: Orientation for Everyone