Well....ok, here is my advice....I personally feel that if you are able to breast feed your son than continue to do so. I'm not sure what kind of job you have, but you should know that pumping and being allowed to pump at work is and should not be a problem. There are laws that will allow you, especially if your employer is not fond of you pumping, that you can present to him/her saying that you are allowed to do such. Contact LLL (La Leche League) for more information about this.
Why is your son not liking the formula? Well duh, it's not you! He's had the luxury of having his mommy give him the best stuff in the world for him, and now you're taking it away from him. You tried to give him a bottle and he refused, well, probably because he could smell you and wanted you instead.
Also think supply and demand, as you start to give him formula instead of you, your supply will decrease.
I personally am against formula, unless your supply is less than adequate for him, but choosing to give him formula instead of what you naturally can give your son, and what is the BEST for him confuses me. Keep trying, keeping pumping, keep giving him the very best you can. It may be hard, but you've made it 6 months, keep going, at least till a year. Good luck.
A.