Good lesson on why safe words are important. I usually just use the stoplight system. Call yellow for uncomfortable but continue or unsure but continue, and then red for stop. I periodically check in if I see physical signs of discomfort and say, "Give me a color," to gauge where my partner is at. I find that this tends to help alleviate any awkwardness or shyness from being honest, even if it may "break scene" a little.
I do like some softcore stuff. Porn proper tends to lack the kind of mental engagement I need.