I have been trying to get my daughter to take a...

I have been trying to get my daughter to take a bottle since 7 weeks old, she is now 4 1/2 months, initally I thought it was the bottle and brought every bottle etc under the sun, however she will quite happily drink boiled water from any of the bottles that I have brought so I feel that it is not the bottle that is the problem. I have also tried many of the formulas but she will not drink it. Everytime I try and give her a bottle or formula or EBM she just seems to chock on it and then starts to cry!! I have even tried to give her formula/EBM in a sippy cup and she does the same thing. I have tried going a long period of time cause everyone says once she is hungry she will drink it, but she doesn't. It is becoming a little frustrating as I need to return to work soon.. I am feeling a little helpless at the moment cause everyone says perservence is the key but I have been trying for ages with no sucess... any sugestions/ideas appreciated.