how can I get my son to quit nursing?

Well my baby is now 14mths Old...and I am still nursing him. It is the best choice, but I feel that it's time to get back into work to get my own income. the problem is Im havin a hard time getting my son to take the sippy cup or bottle. he takes them fine when we are eating at the table, but when he's with a sitter he won't take them at all...and there are times when he'll only sleep when he is being breastfed. I hate to see him cry and feel bad about trying to make him stop but nursing does take up a lot of time, especially now when his appetite is growing. 

Can anyone share their story with me if you had nursed your kid/s and how you were able to get them to stop??