You sound as though you have had a very interesting, successful and versatile working history, and it would be a shame if you glossed over what you have achieved. You have to write your resume from the perspective of the person reading it. Don’t assume they know anything! They don't know anything about you or your background, so you need to have a ‘reasonable level of detail’. So what does that mean?
Ask someone who doesn't have a detailed knowledge of your working history to look it over for you. They will be able to tell you if it makes sense! List your different roles under each company title (reverse chronological order please – i.e. most recent job first), and it should follow that each role is a progression from the last. Highlight your experience in bullet point form (essays are usually too long-winded and harder to read quickly), and quantify and elaborate where necessary.
For example, ‘preparing monthly reports’ needs to be a bit more specific. If your resume is about 3 to 4 pages, it won't be ‘big and boring’. Remember, it may be boring to you, but could be very exciting to your next employer.
Have a question for Manda Milling, people2people Director? Let us know in the comments or tweet @p2pManda!