The book recommended by fruitporn is good, that explains things well. Also try and invest in pharmaceutical practice by richards and winfield, its got a whole section dedicated to it.
Don't drop out, you are still passing and let me tell you, the degree class doesn't matter and your first year doesn't count anyway. You have to stick in there.
In 2nd year you get a lot of free time off in all essence but just have more to read around. Pharmacy can be hard but if you stick at it it really isn't.