How do I figure out my gender identity after doubting myself?

It's a different journey for everyone, but you can start by wondering what each label ("man", "woman" and so on) means to you. Gender is a socially built concept, and everyone draws on this concept in their own way to figure out the definition that best describes them. It's about what gender means to you, not about how you fit in a pre-defined notion of gender. Of course, you can experiment as much as you want by pondering different names, pronouns, gender expressions. You can also reach out to people who have been through gender questioning as you are right now, and listen to their experiences. But ultimately, how you identify is up to you.