Can I go back to being cold and emotionless now😭❤️

I'm 16 and a sophomore in high school. I'm friends with a girl named Sarah and she has an older brother, I've only hung out with Sarah a few times outside of school but I have never really talked to her brother. Well about a month ago her brother started going to my high school again (he was previously homeschooled). He got put in my PE class. We never spoke. I knew who he was, he kinda kept to himself and I never said anything because I'm really shy. About 2 weeks ago he messaged me on Facebook and asked if we had PE together, I said yes and we made conversation. A few days later her texted me and said he had something to tell me I asked what it was and he told me he had feelings for me. At first I didn't know how I felt about it but as time went on I developed feelings for him as well. I told him it was important that his sister (my friend) knew and was okay with it. I told her and she had no problem with it. He has been nothing but sweet and amazing to me. He makes me laugh. He makes me feel beautiful every single day. In the past he has been known to be the kind of hi that got into trouble and didn't care about school or anything. But since we've been talking he's trying to do better. This problem seems crazy but I love him. It was fast no doubt about that. Last night I was hanging out with 2 of my friends and he asked if I could come hangout. So me and my 2 girl friends drove out to where he was when we got there him and his friends were sitting on the porch. I didn't know him friends so I didn't wanna just walk up to them so he walked over to the car and I got out and hugged me. Omg in that moment everything stopped he was the only thing I was focused on. We were on the tailgate of my friends truck talking and we started making out things got a little heated lol but I stopped him and told him I wasn't ready. He was totally okay with it and was super respectful about it. I wish I could stopped feeling this. But I love it all at the same time. So what does it mean when I guy goes from getting in trouble constantly to doing his best to change for a girl?