Am I loosing a best friend?

We made plans to go to to a festival with friends and he went early after school. I texted and called and he never answered back because I wanted to know where he was so we could meet up. I figured his phone was almost dead, so me and my friends went to look for him. After a while we found him and when he saw us he got up with another friend jamie. He started to walk away. I ran and slapped him on his shoulder playfully saying hey. He just said hi like he was nervous or he barely knew me. Je continued to walk with jamie. He doesnt look at me and says," Oh this is my friend mim." He was's till walking away and never bothered to look at me. He said this like he was forced to say it or didnt care. It hurt and thw whole time he never tried to find me and our friends. I still havent heard from him and this was like yesterday. but hes been kinda different. Though to but not majorly but r these signs that we r starting to part, seperate. Become just friends or somebody he knows?!