Nausea, Any ideas why?

Now that MRI is clean for mets, and I'm still having intermittent nausea, I thought some of you might have a few ideas. I only have two herceptin to go, and I always have diarrhea after, but it has gotten worse as time goes by. (Great sitcom "As Time Goes By," on BBC)

My husband thinks the nausea is herceptin, but I don't. I have a bit more reflux now, but nothing like it was years ago, before medication, and even then I never had nausea. Also, my BP seems to have gone back up again. It was quite low for a while with dystolic in high 50's to high 60's. I take BP medication but it never brought it down that low! Any thoughts on either would be appreciated. Doctors tend to shrug their shoulders but I always believe there's a reason for everything.

Thanks.