How's it going helenabeth? I've been following this thread and wondered what the health visitor said. my DS2 was 4 in March and I visited the GP a couple of months back because his eating was so bad (not that she was bothered as somehow he seems to keep growing, although only just under the 25th centile). His fussy eating started the same age as your son too. They sound quite similar boys.
I just wanted to offer you some hope really. When my DS was your son's age I used to read posts from people like me that said "There IS hope - one day he/she'll get better." and I used to get really fed up because I really really couldn't see my son EVER changing. I know exactly how you feel about finding it so frustrating that you want to cry.
But just in the past few weeks there has been a huge change and I really don't know what the reason is for it, I am just so happy that the turning point has finally arrived. Prior to the magical day when he actually bit off a corner of fish finger and swallowed it, he would only eat 2 types of main meal - pasta with a blended-down sauce (at least I could put vegetables in I suppose), or chilli and rice (again, with the sauce blended so there were no "bits"). He never had a proper bit of meat or fish of any kind without it being mushed up and hidden in some sauce with rice etc and has never touched fruit (smoothies only).
For lunch he would only eat ham sandwiches or cheese on toast. Dessert was only yoghurt, chocolate mousse or cake.
He hasn't touched milk since he was 2.
Anyway, apart from amazing everyone in the room by eating a bit of fish finger (dont' know what prompted him to try it instead of the usual recoiling in fear), he seemed to amaze HIMSELF and I honestly think that he finally realised that there was not that much to worry about in just TRYING a food. We've told him that we wouldnt' expect him to eat a whole fishfinger/whatever till he is happy to do so but he still has to have a bit of SOMETHING he doens't normally eat at most main meals. And we decided to reinforce with a star chart and promise of a trip to a theme park once he gets loads of stars (haven't figured out the exact number yet!)
Honestly the change in him these past few weeks is astonishing. I just think that he has just reached a point in himself where he'd like to try what other people are eating. He has been trying pizza, beefburger, soup, thai curry sauce, baked beans, loads more - actully ASKING to try some things such as a big bit of mushroom from a pizza etc etc etc. Each time he has taken a bite and actually swallowed it, not spat it out or baulked. I can't tell you how pleased we are even at these little bites of things - it may not seem much to outsiders but I know that other parents who've experienced this will know what I mean when I say it has changed our lives! (well, taken the stress out of mealtimes anyway!!)
We are still not getting anywhere with fruit (he baulked at just the smell of a strawberry the other day, strange boy!) but we're taking it one step at a time to build his confidence up even further.
So, even though I know that right now, you probably just can't imagine that ever happening with your son, I just wanted to say that a change IS possible - I think in children like ours it's all about them finding the confidence in themselves to start trying things and it may not come until your son is quite a bit older.
And obviously it gets much easier when they are older and their language skills improve and you can explain all about the food and what treat they might get if they start trying things!
It is sooooo hard, I know, and I still get a knot in my stomach at meal times wondering if this is the time that he'll revert back to how he used to be, but any time he's wavered I've reminded him about getting a star towards his treat day and it seems to work!
Hope that's of some comfort, however little!
Let us know how things progress, I'm sure you know you're not alone in experiencing this (and I know how fed up you probably are at explaining the situation to parents who have never had a child like this and give you the impression that they think it's something that YOU'VE done wrong).
Best of luck!!!!