Probably bosses feel that you are very efficient and use time well to plan and do your jobs well.
Normally efficient people are tasked more because of their ability and also time management skill and job prioritisation skill.
Probably you need to record each job you are doing and if more jobs land up than possible ,then do inform your bosses about the position of each job.
Boss may not be fully aware of the nitty gritty of each job and you will have to explain to him and keep him posted on job status.
Every job is not single handed jobs and you do depend on inputs from others.
Explain these facts calmly and proceed.
I appreciate your valuable and supportive feedback, but let me add here one thing that i tried my best to explain but i experienced that he is not focusing on it and a bit later he makes follow up on which i already submitted my explanation.
But, I will surely try as u suggested on a better way.
Steady and timely work as per acceptable quality is what matters.
Have a clear record of the jobs you do.
When given jobs beyond your ability due to over load, make it a point to prioritise the jobs and ask the boss which to do first or ask for a different timeline.
There is also danger of making a job look too easy also.
Simply be meticulous in your work and the organisation should be certain of your reliable delivery of product/output.