Is there a reason why you're adding "I'm retarded!" there?
Technically, if you are referring to yourself with well-meaning intent, and this is something honestly meant on your part, 'retarded' isn't the word to be used; if you've an intellectual disability--there are better terms to describe yourself that way (as in if you're attempting to let others know if you have an impediment that affects your understanding and you're saying you're retarded as a note for understanding, the term 'retarded' has been replaced by intellectual disability, because of how...crude, 'retarded' sounded.)
In a way, it may also come off as trolling since you seem to have several adjectives denouncing yourself on your profile, like:
Personal Text: Lord of incompetence
So to forum-goers, it looks 'off', as in it looks strange for someone to be having those labels (even if considering you may have ID--the acronym for intellectual disability, calling yourself these terms are not common or expected).
Unless you're merely saying "I'm retarded" for any other reason (ie You've been mocked or teased for a long period of time, rather than diagnosed or otherwise)--it's better to mention the reason behind why you're saying so. If otherwise, it's best to not mention it that way, or whenever you feel the need to. You can just ask instead for people to explain clearly.
Basically, in general, people don't know why you're saying "I'm retarded", and that along with several other things (ie That personal text) can give off ...not a good impression.
While well meaning, I can see how this is expecting too much. If a person, for instance, has a severe handicap with language, expecting them to call themselves "Linguistically challenged" is silly. It expects them to perform a feat that is not really within their grasp. Instead, they may say "I not good with words" or something similarly simple and contrite. Some might consider this offensive, due to Poe's Law, believing that the individual is lampooning a challenged person with puerile intent.
Likewise, a person with a severe cogitative handicap, may refer to themselves as "retarded", because the word is easy to understand, and widely known, despite the negative associations the word carries. Due to their handicap, expecting them to use a more clinical and thus less emotionally loaded term is a non-sequitor. That's like asking a double leg amputee to stand up.
Further, the person who really does have such a handicap might not be capable of understanding the fullness of the negative association of the easier, well used word for the issue, and thus may genuinely and truly not understand the sanctions placed on them for using it.
In our zeal to silence people who use the word hurtfully (to stop the hurtful intentions), we should not cause emotional harm to those that use it innocently.
One of the many reasons why I greatly detest things like zero tolerance, and the kinds of convoluted thought that political correctness produces.
I especially dislike the "It offended me! I am offended even though I dont have that disability because somebody used that word! Therefor TROLL! No exceptions!!" mindset that often accompanies these things, because they are very much anti-victim, and pro justice-warrior in nature.
Remember, just because something might have offended you, does not mean the person who did it meant to be offensive, and when the only road to avoiding being offensive is to force the actual victims into an impossible situation, it is doubly unacceptable.
I know you are a good person Tiruin, and would never consider doing such things consciously. I just ask that you be more mindful of what you did not intend, much like thread's parent, ironically.