Once you use past perfect, do you have to use past perfect even for an action that happened simultaneously?
I sent you an answer yesterday. Remember? It's the answer to the question you had asked me about since you had trouble answering it.
For this "had", should I use past perfect or is past perfect implied here because I said "had asked"?
EDIT: I don't think I made this edit very noticeable.
For example, in "I have checked your email and forwarded it to X," the "have" is implied, right? Both in writing and speech, people will understand that you are saying "I have forwarded it to X". If I were to write my first example instead of saying it, is the "had" implied in the "had trouble answering it" part? (Once you backshift, do you no longer need to backshift or do you have to backshift every single time you mention a past perfect action?)
I mean, how can I distinguish between 1) the person first had trouble answering a question, so he/she asked me a question and 2) the person having trouble answering a question and he/she asking me happened around the same time. Or is this distinction not very necessary since I'm not writing a book or anything?