Will try keep it simple ,

My girlfriend of 6 months went out with her friend last night , we spoke before and arranged that I would pick her up after , asked her to keep in touch ,. She doesnt text all night and 2am comes the club closes , i phone her between 2 and 2:15 , no answer. I drive to town where club comes out and phone again but no answer. I go to club on high street and see my girl drunk and sitting down in street. She doesnt seem all there and isnt bothered when I arrive. I ask her if she wants to come home and she says no , usually we spend saturday nights sundays together. She hasnt been in touch since with me since 2am last night and hasn t bothered to call or text. Why sudden change of feelings towards me. It seems shady behaviour and has blown all my trust in her. I havent done anything wrong and she knows it will be hurting me. She has caused unecassary dramas and fights with us before but usually resolved and back to normal soon. I didnt contact her at all today instead hoping she would contact me , still nothing I tried texting her a short message asking what I had done but no reply. Im heartbroken , worried , confused and dont know what to do?

Any help is appreciated