Please don't worry about the comments from the ultrasound man - as I understand it ibc is a 'diffuse' cancer, which does not come up as a lump. Most other breast cancers will show one or more lumps, but ibc grows in 'sheets'. I am an IBC patient too, mine did not show a lump either.
When I was first diagnosed I was worried about all so many things that doctors or consultants said, and only much later I would realise that the things I worried about were pretty normal. Well I mean normal as far as normal goes with all this breast cancer diagnosis and treatment etc. As you rightly say, it is all so hard to take in, especially when you have just been given such a shock diagnosis so recently and are now thrown into the treatment with such speed, not knowing yet how it will affect you, nor all the steps that you will have to go through.
I am happy to hear you have started chemo so quickly, and wish you the very best with your treatment. I finished my treatment a little while ago now. I did find this site and the Macmillan site very helpful - both the forums and the Macmillan telephone service were fantastic (still are).