There could be a number of things going on.
First, as was already mentioned, you may have a sensitivity or allergy to one or more of your soaping oils. I can use coconut oil up to about 20% and then my skin isn't happy, regardless of the SF I use.
Second, you should calibrate your scale. Also if you are measuring in ounces or 10th of ounces, try measuring in grams for greater accuracy. How large is your batch size? Smaller batches are more sensitive to measurement errors.
Third, I can't remember if you mentioned fragrance in your soap. You might try fragrance-free.
Fourth, you might want to raise your SF to 10 or even 12%. I know a soap maker who has very sensitive skin and she needs to SF at 12%. Her soap is the best I've ever used, better than my own, and it never gets DOS.
Finally, and this is probably sacrilege on a forum like this one. Some people have skin that does not tolerate CP soap well and they do better with a detergent-based bar which has a more neutral pH. I know a few people like this and they formulate their own cleansing bars with surfactants. If you have used CP soap from other soap makers that you tolerate well, then this is probably not the issue. But it is possible. Before giving up, I'd try a 100% olive oil soap and see how that works for you. It will have to cure a good long while but if pure Castille is what works for you, it would be worth it.
Hope this helps!