I don't know if I'm in love with my best friend and if he's trying to flirt with me. How can I be sure?

So, I'm f18 and my best friend (m18) Max, have know each other for three years. We've started to be friends because we each got one of our respective friends to date each other. We'll call them Joe and Mia. Me and him got along and became good friends. After a while, like two years of friendship, he started to make jokes about my chest. I don't mind the jokes, they're funny and if I don't like them and want him to stop, I know he would. Anyway, he started to make jokes about that. At first, it was just all verbal jokes but after a while, he started to makes jokes about groping my chest. Again, I didn't minded. I just brushed it off as a ''guy's joke''. I've always found him kind of cute. About my height, messy hair, funny, playful, etc. But I was never interested in him. He was just my best friend. I think that everything changed yesterday. My friends and me (Joe, Mia and Max) for Halloween, decided to go at Max's job to wait for him and do a movies marathon at Joe's house. Joe and Mia were to sleep on the mattress that was on the floor and Max an me shared the couch. You know like the couch that look like an L? Well, we each got our side. We watched movies and everything and at one point, he came closer so that I could pet his hair. (I asked him to) I was wearing a crop top and shorts (wich were really shorts) I was getting cold so he passed me his really big hoodie. I was laying on my side in like the foetal position and my thighs were exposed. I thought nothing of it to be honest. Joe and Mia were already asleep. At one point, he started to stroke my thighs. You the couple in the movies? Well, it looked like that. I got chills down my back and started to feel weird but a good weird. During the evening, he also was able to grop me. I kinda fought against him but I didn't minded. I wanted this. And now, I don't what to think of our relationship. I think I love him but I don't understand what his doing mean. I'm completely lost. Please help me.

I don't know if I'm in love with my best friend and if he's trying to flirt with me. How can I be sure?
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