Friend problems? :'( I don't know what to do..?

right I have three main best friends, they are my life and i tell them everything. but today i was with one of my best friends and the other two were starring at me in a horrid way. I smiled at them and they turned away. so i went and sat with them and they just turned the other way and talked to someone else. so i was like mmkay, so i just joined in the convo and they ignored me. And i was sitting in the canteen before talking to one of them, and the other two came in and said ' come on '.....' and she walked off with them. I said hey guys wait up and they just walked off, sharing jokes together, laughing. they know im going threw a tough patch right now with one my family members being ill :-/ I am genuinely upset, i have done nothing to provoke this!: '( what can i do???