I am not an expert, but I think that you have done a very good job.
I felt extremely tired yesterday, so I drank a lot of coffee. ["A copious amount" IS excellent English, but Americans usually do not use such formal language.] As a result, I have been suffering from severe diarrhea since yesterday evening; therefore, I have to apply for one day's work leave today. I really am not sure whether I am fortunate or unfortunate, for I found a new website yesterday afternoon that taught me some new words. The only thing that I regret is that my cellphone will not work because the battery _________________.
I do not understand your use of the word "spoiled." Do you mean you have to recharge your battery? Do you mean that you have to buy a new battery? (P.S. We usually do not say "My heart is quite painful." If you want to, you could say "I am very sad / distressed / upset.")