Sounds like you two have still haven't got the communication lines open anymore than before!
How often have you been in contact since October? If you were thinking of moving in together when you got back then sounds like you are in a full on relationship and it maybe that your downfall here is that you are not discussing this with her. I understand that you need to be there for your mother and you feel you are needed there but you booked for 4 months and then you cancelled out on going back and have told her you don't know when you are returning. Was there any discussion here?
For all she knows you are having the time of your life and making excuses. You're definitely not considering her feelings if you haven't taken her thoughts into consideration.
If you want this lady, perhaps you should actually try talking to her and listening