Losing my virginity

Ok so I'm 17 and I've been knowing this guy since 3rd grade. We've always been really close and we were nothing more than friends... Until the 8th grade that is. I started developing "more than friends" feelings for him and I know he feels the same way about me. We're now seniors in high school. Over the summer we hung out and stuff. One day we went to the mall and spent the day together; including my best friend. He left the mall before we did but told me to come to his car with him. We basically made out and got a little touchy feely with eachother in the car. Afterwards I couldn't stop thinking about it. This was in June. It is now August. Every time I get around him I get a little.... Happy; if you know what I mean. I honestly trust him and feel like he's the one I want to lose my virginity to... But here's the problem... My sister and mom always try to explain sex to me. They basically tell me it's gonna be the worst pain ever BUT all of my friends that are doing it explained to me that their first time wasn't all that bad... Honestly I just want to know how do I prepare myself mentally and physically for this huge step I'm about to take. Someone please give advice❤️