Why has he changed so much ?

i was close friends with a man for two years. this year ive seen him change a lot. he lies to me about stuff and it hurts as ive been a loyal friend to him. hes snappy and moody a lot when i ask if anythings wrong he says stop asking we used to talk loads now hardy ever. we're both on a new team at work with more people and he worked with me before now hardly ever and i still do loads for him but he never appeciates it. he also knows im hung up on him and he makes me call him now like i have to chase him. whats the best way to handle this please help