ready to settle with boyfriend ALREADY!?

Okay so me and my s/o have been with each other for 5 months. I’m 17 next month and he’s 18 (19 in May). I know it’s so early to think about our future and stuff but I really feel like he’s the one. I’ve had past relationships and I’ve never felt anything like this before. We’ve talked about marrying each other and having kids. It seems extreme but our feelings for each other are so strong. Am I being dumb or is having these feelings this early on alright?