We don't know but they will find out. What we do know is that the big one you fear would have made you very ill by now unless you are some unheard of medical miracle. But whatever they find, you will cope. There is little choice and whilst it may feel the end of the world at first you will find a way to accept things because what other choice is there?
The time is here now. Anticipation anxiety can be taken over by "just getting on with it". The waiting up to this point is always where anxiety runs rampant.
But tell them everything. Don't leave out what you have been experiencing the last 12 months or so. And I mean everything, the worms included. They are not going to judge you or being embarassed...they spend their days up people's bottoms! Write it all down in bullet points so you can get it all across. If you leave stuff out you will oly be back on here with "what if they missed xyz because I didn't mention...", we see it all the time