What's wrong with my Sony Ericsson Xperia Arc?

[mmmmmmmz_gmml_10m]

So my phone has 350 MBs of internal memory and 32 GB external memory. I literally have NOTHING downloaded on the internal memory. However it says that it has low memory therefore for some reason I cant download/update anything (36 mb free) it used to have about 150 mb free. Is there something I don't know about where app or something automatically downloads onto the phone? Please help.

 

[Mark]

Yes:
- Go to settings
- then to applications (sorry if it isn't exactly labelled that way, my phone is in dutch)
- memory usage
- You will see all apps, click on of of them and select: transfer to sd-card