Vesper, I'm not sure which IQ tests you have taken, but most professional tests have been shown to be extremely reliable (validity i another matter).
Please, please, please, pleae, please everyone put no stock whatsoever in the results that an online IQ test spits out (I aume you're all savvy enough to know this anyway). Often, even when sites claim to have an official version of some IQ test, they feature variou items ripped from the test and presented out of context.
To obtain a valid measure of one's IQ, you need to administer a test that has been validated for your individual's population group (by nationality, ethnicity, age, gender etc), and you need to be qualified to administer that test.
I do agree that IQ tests are largely useless. They can still be used to identify individuals with inhibited functioning in certain cognitive abilities, but they are still at times used for screening purposes in job interviews (which is wrong) and are associated with a person's 'cleverness' instead of being recognised as a specific measure of a series of cognitive abilities.