There is some doubt there. Otherwise, there would be no need for personal affirmation on this. Get yourself a girlfriend, then the truth may reveal itself.
I'm straight male but why do I feel like I need to know that I AM for sure? (people kept being mean and saying that I wasn't and I think that could be a cause but please help me)
You could be Bi Curious, it's when you are curious of having a sexual or romantic relationship with another gender other than your opposite.