How do I know if Im really trans?

Im a biological male and I've alway wanted to be a girl and have been closeted for 17 entire year. I have now recieve the privilage to be able to take HRT treatment and other gender affirming surgeries. I've only discovered that Im apart of the trans community around 3 weeks ago before that I just thought that I was just gay and that wishing I was a girl was just a part of being gay. I've also found out that I don't want to appear gay, I want to look exactly like and fit in with the girls. However certain event has made me doubt my transgender, I know that Im REALLY want to be a girl but what other factor could have contribute to me feeling this way?

Factor as in:
past sexual assult trauma
misleading and misinformation on social media

is there any other factor?

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This doubt about my gender has made my dysphoria even worse now. I can't be sure of anything anymore, I don't know if I can trust myself. What if I want to de transition? This feeling is so f$^king terrifying and uneasy. Im I even making sense?