Too much work....

Don't get me wrong, I like my job a lot...but the amount of work that is coming in is starting to wear on me. When I was promoted/upgraded to Project Manager earlier in the year, I was responsible for 1 gigantic project that had 3 phases (each of which was as big as a single normal-sized project). Once the first two phases were complete, I was given another project...and another...and another. I am now up to 6 projects (including the 3rd phase of the first giant one).
I appreciate that the people I work with trust me to do a good job, but it's becoming a little burdensome. My very capable and hardworking officemate Jessica still takes the cake with 8 projects, but I'm quickly catching up. We have 5 Project Managers here. Here's the breakdown for number of projects by manager:

Jessica: 8 projects
Me: 6 projects
Michael: 2 projects
Jeanine: 1 project
James: 1 project

Something seems a little off, huh?
I, among others, are very curious (heading towards angry) about why this is the case. If the powers that be don't want to give projects to certain people, why are they even here? Get rid of them and bring in someone who can do the work.
Sheesh!