To add to Henning's excellent answer, if you really wanted to use the "I'm X of that" construction, I can think of three words that will fit in place of X there:
I'm aware of that
This one might sound quite neutral on the face of it, but it's actually quite easy for this to come across as slightly sarcastic; the unspoken implication being "well obviously I'm aware of that". So be cautious especially when using it in textual communications, but even when spoken aloud be careful about your tone of voice when using it. The advantage is it does sound quite natural and I would expect to hear this in both informal and formal speech.
I'm conscious of that
This one seems genuinely quite neutral to me, I don't think it could be misconstrued as sarcastic so easily. It does seem slightly more formal/"businessy", in that I wouldn't expect it to be the sort of thing you'd say to your friends down the pub, unlike the above; but still works in a variety of cases.
I'm cognizant of that
"Cognizant" is a bit of a rarer word, so this one would definitely be for more formal contexts only. It also has the danger of it seeming like you're using a fancy word deliberately to show off your vocabulary; if the rest of the conversation uses long/unusual words it's probably fine but if not, I'd avoid this one.
I'm a British English native speaker which is basically the source of these feelings, but I doubt American English differs significantly on this subject.