Sometimes the word help is inserted to convey this thought:
I couldn't help but notice that ketchup on your chin.
The leading words can vary; one might say I can't help but notice, or he couldn't help but notice. Cannot and could not are sometimes used as well.
You can find several instances of this phrase if you peruse this list.
An Ngram would suggest that this particular wording is relatively contemporary, at least in terms of its popularity: