I agree with most everything people here have said with some comments.
I've had various black teas for years and they will actually improve
the older they get. Black tea doesn't really go bad, IMNSHO, it just loses a lot of flavor.
My guess is that you're using too much tea for the water, steeping it too long, not doing a flash rinse (with boiling water), not the type of tea you like, or the tea is just bad or really poor quality. I've had some pretty bitter keemun tea where I've actually had a better leaf the year before from the same brand. So, a lot depends on the crop and harvest.
Here are some thoughts to try to make the tea drinkable:
Flash rinse the tea before steeping it. I rinse the leaves quickly with boiling water before I try to steep them.
Either try less tea for the amount of water or reduce steeping time.
Add a small amount of sugar. Sometimes sugar tames really skanky tea.
Brew the first batch and toss. Try a second steep with the leaves and see how that tastes.