That is your anxiety talking - it does things to the rational part of your brain and stops you from thinking straight.
Ive just had a poke around at the side of my back - i can feel a hard lump, its one of my ribs! I would be very surprised if you could feel anything from a liver tumour at the back. Also, if you had a tumour that was big enough for you (despite being a health professional i suspect not a dr), with no experience in what you are looking for to find it, on your liver, you would be displaying a whole range of other symptoms by now and you aren't.
I don't mean to sound harsh but i just have been where you are (similar) I was hysterical because i thought my tonsils were tumours, I also have a medical(ish) background. My dad always used to say, a little knowledge is a dangerous thing. He was right - add Dr Google into the mix and you are in a world of shit.
The good news is you don't have to live like this - there is help available. If you are scared of going to the Dr, can you take someone with you? Also, you could write down your worries and then you don't have to say anything.
Two good things will come out of a visit to the Dr.
- He/she will put your mind at rest
- You can get some medication the HA and you can be put on the waiting list for CBT.
You can take control of this and stop letting anxiety rule your life.
I still get anxious, in fact, most of my life is spent on one level of anxiety or another but im fucked if im going to let it ruin my life - i take medication and probably will do forever, but it works (most of the time).