Help!! Toilet problem in Singapore

I'm not too sure about the details and I don't know toilet terminology well so please bare with me. I live in Singapore and my toilet is having a major problem.

It seems that my shower and toilet are connected and its usually after a shower or after a flush that the "problem" arises. That thingy with holes and can be opened and closed on the floor will emit water. I think thats called a drainer and its supposed to drain water but instead, what i am guessing is that the water travelled up through it instead and flooded my bathroom. My father insists that its due to the toilet getting choked most probably because we use too much toilet paper to wipe our waste. This has happened once before and we hired a plumber. All he did was to suck up everyone from inside the "drainer" thingy and clean the bathroom floor.

However i am pretty sure that the problem isn't that simple. Previously we had THREE people using the toilet and for a few years that didn't happen till recently and we had only TWO people using it now. That doesn't make sense. My father just rationalized by saying "the pipes old". WDF? The pipe doesn't go through such drastic shrinkage, no such thing at all. Modern pipes are designed to ease thermal expansion(if it isn't, it would crack instead of shrinking permanently) so i don't think theres a problem at all and i don't see how it can shrink. Although choking is a major contender of this problem, i think it might be something else. My father refuses to listen to reason and blames it all on me and refuses to hire another plumber. Please help!!

I live with a wife so I can work with "thingys" and such, but the rest of the description of your problem leads me to assume that the plumbing facilities in Singapore, to be as gentle as possible, are not exactly the same as in the US. I don't know how much help any of us can be, but pictures could possibly help.

Sometimes, it's simply something that has fallen in the bowl, and is "hanging" things up.

Nvm my father hired a competent plumber this time and he said theres some "water" problems but i'm not too sure about the details i just overheard. Ty for trying to help anyway. I think our toilets here are almost the same as yours. Forget i said anything if it doesn't make sense. That "thingy" or drainer if you still don't get what i mean is this:

http://www.showy.com.sg/bathroom/2385F.jpg

That appears to be some kind of floor drain cover. There should be a trap in the drain that it covers. It is just like any other drain in this respect. A clogged drain will fill up and that water has to go somewhere. It will come up at the lowest opening which in this case would be the floor drain. What is called for is a plumber that can auger (snake) the entire drain. The requires equipment and know how that is beyond homeowners, so be be fooled in buying/renting a small hand operated device. They typically will either just push the clog deeper or just poke through it without clearing it. Also, forget about chemical drain cleaner or openers. These are not effective on clogged sewer lines and can create a hazard for the plumber who will eventually have to be called. Once the clog is removed, then the mess on the floor can be washed through the floor drain. See, the photo helped a bunch!

My interpretation is: almost sounds like he has a floor drain, the main line from the toilet is clogged and when flushed, backs up the main and comes up the floor drain (or possibly shower drain).

I would agree! You need to have your main sewer line cleaned.