You used a whole cake? Pu-erh is potent. I would have been up for days.
I collect and age Pu-erh teas. This tea is truly wonderful with some age on it. I use a special tool that looks like a mini letter opener. I just insert it into the beeng and simply pry out a clump of tea. The key is to do as little breaking of the leaves as possible. This reduces the bitterness of the teas. I also try to seperate a bit of the clump without destroying the integrity of the leaves.
Most Pu-erhs with less than 3 years of age are undrinkable to my palate. They can taste very "farmy". Fishy taste can often be from a poorly stored beeng. With that said, Pu-erh is like a wonderful hybrid of tea and coffee. It certainly doesn't taste like any tea you are probably used to but has some herbal themes you don't get with coffee. Pu-erh though has a fuller body than any tea I have ever drank. It takes some getting used to...make sure it has some age on it then work on how you break a beeng down. Also, steeping takes a little practice and observation. Steep too long and it become undrinkable. I usually do a couple washes. Then the third I will steep no longer than 10 seconds. Right beeng, with proper age, with proper technique and you have an unreal tea experience. It's well worth the time, money and research.