Can you mix spermicidal lubricant with K-Y Yours + Mine lubricant?

I'm wanting to see if it's possible to mix spermicidal lubricant with the K-Y Yours + Mine lubricant. My girlfriend and I want to try the K-Y, and we hate condoms. She's on birth control, but you can never be too careful. If we add a bit of the spermicidal lube, then add the K-Y, will we still get the same sensation that it's supposed to deliver? We want to be safe, but we both HATE condoms. Does anyone know if this is an acceptable combination?