You need to break up and move on because no one is worth it if this is how you feel. If you're walking on egg shells now it is only going to get worse the longer you're with him. I've been through it all myself.

It means there is no use of acronyms, abbreviations, jargon and slang words. Making sure your information is clear to understand and that it can not be misinterpreted in any way. There are organisations which will proof-read documents for you to make sure it's clear and is in plain English.