Multitasker

I'm supposed to hand on the accunt reports to my boss today.Unfortunately,i haven't finished it yet since i was so bz last week.I planned to finished it by last saturday.Then came my project manager with a new task.He wanted me to revise the cpm of work programme for banting project.I thought i've submitted it to the main-con's qs a few weeks ago.He told me there will be a meeting with jkr on tuesday (tomorrow).So they need to update the cpm.The problem was the qs has no idea how to make the cpm.What?She didn't know how to make it?She's a qs.She's supposed of know about it.'Malu la qs tak tau buat cpm'.Even i know how to make it even though i'm not a qs & i've no technical background.He always like that.Last minute.He always asked me to do last minute task until i've to put aside my main tasks.
My project manager asked me to teach & assist the qs b'coz she has no one to teach her b4 this.I'm also have no 'teacher'.I learned it on my own.I admit i'm not that good about it but at least i can make it.I'm really bz right now & now he wanted me to assist her.But when i called her,she needed me to do a lot of it.She 'complained' that the cpm can't be updated automatically when she updated the progress.Sure bcoz' last time i did it manually since i thought she know how the cpm works.So,i've to redo the programme from the beginning.What make me furious,she needed it by that noon (saturday noon).I've to work until 5 that day with no pay.Then i e-mailed it to her.
This morning my project manager called me again asking the progress of the cpm.I thought i've e-mailed it to her.Actually she has received it but as usually she needed me to adjust a few things more.Why can't she figure it out herself?It was only a minor adjustment.It was her job.
Sometimes i feel that the life is unfair .I've to do other's job but they'll get the credit.Whereas i've to work overtime with no pay to finish it & the worst thing is i've to put aside my own tasks.Sometimes comes to my mind,what the hack i'm doing?What is my position?I'm only an administrator but why on earth i do the qs, the engineer & other technical's job?We have our own staff in that area but in the end i'v eto do it.I'm so proud of myself of being a multitasker bcoz' i know most of the job here in my industry but sometimes when my own tasks are mountaining,i needed someone to understand my situation.I've complained it to my boss & my lady boss, & the understand it.But the problem is others like my manager.My lady boss told me to complained it to my manager.Oh no.I can't do that.He's my manager & i'm not that closed to him.He should understand my situation.I had to all things on my own including his job (he has his own company at tha same time).But i understand that people always like to take for granted.Oh,when will my boss find a new assistant for me?I need help!