It will get better, as most everyone as said so far. My son bit as well, and we nursed for 2 1/2 years, so I promise, the biting stops. Don't make a big deal and scream and yell and stick him in his crib to cry. You don't want him to associate the breast with anger and upsetting you. He isn't meaning to hurt you, so why get mad and scream at him? All that does is scare him, and can cause a nursing strike. They don't last long, but it's still uncomfortable.
There's no reason to start pumping and giving a bottle, unless you plan to wean early, because you won't be able to keep up much of a milk supply with the pump only.
Like others have said, watch him closely, because when he bites, he isn't nursing. It's probably the end of the feeding, when most babies bite, if it is, start paying attention to the signs of when he's done eating and he's just sucking. Take him off. If he does bite, take him off, say, No, don't bite mommy. And hand him a chew toy. Lay him down with it. Come back in a couple of minutes and try again. But be calm about it, again, there's no reason to scare him and make him think he's done something so terrible you're angry with him.
Even though he's only 5 months, he understands. He can understand when you're angry and upset, and trust me, that isn't waht he wants. And he understands when you mean business. You just let him know that biting isn't acceptable. He'll soon learn that when he bites, not only is the breast gone, but mommy walks away too. And because you're handing him something to chew on, he learns, okay,when my teeth hurt, I bite this, and when I'm hungry I suck on mommy!!
Again, it won't last forever, and he isn't doing it on purpose. Keep it up!!