Hi, Here is some info, from the BTD website about secretor status, and what it means. Maybe you'll get some idea from this?

http://www.dadamo.com/knowbase/subtype/sec9.htm

I think to really work it out without a test, you would need to do a lot of detective work, reading up on beneficial/neutrals and avoids for secretors and non-secretors, and try to work out what does or doesn't agree with you. But, at best this would only be guesswork.

Good luck!

You can do the Blood Type Diet without knowing, just assume you are a sec, for the time being( that's what Dr D says to do)
You can Type in Food List for Blood type O and when it comes to the page with the choices look for the one with a capital K click on it. It list beneficial, neutrals and avoids In blue, black and red. If you could print it out that would be helpful to you both for helping you eat right, and also shop right. I have been on it since last August. So many benefits. Weight Loss,No pain from arthritis, I am no longer using a wheel chair, walker, a cane, or oxygen, I am feeling wonderful. I was on oxygen 24/7 for 5 yrs, 3 months & 26 days.. Best to you on your BTD adventure, it is worth it. I know.