Oh, I think I've had this. I had a real struggle finding a spermicide that worked for me, and then they kept changing which ones were available. I'd have a chat with the pharmacist.
I'm assuming the reaction can't be to the latex in the diaphragm?
I would do a patch test, come to think of it, just to isolate the fact it was the spermicide? Small bit on the labia sort of thing? If you could face it?
(I've had some small reaction to sperm, sometimes, too. It's tricky, it's such a delicate part of the anatomy ...)