The fact that you have been taking Vitamin D supplements tells me that I may be onto something here haha but please check User3532’s theory first because that should take precedence.
Given that you don’t use apps and local PT’s have been unhelpful I’m going to take a wild guess and say that you probably haven’t checked exactly how much Huel you should be taking per day or meal. Now as you’ve pointed out, it already has “something of everything in any way”, but too much or too little could be the cause of your tiredness. My suggestion is to use at least an online website where you can input your details, i.e. gender, age, current kg, desired kg and level of activity and then it will tell you how many calories per day you should be consuming. Once you have that number, you can divide it into a specific number of Huel scoops that you can distribute in 4 or 5 (preferably equal and in fixed intervals) meals. Alternatively and if you only have two Huel meals per day, decide what proportion of your diet should be covered by Huel and then estimate what the remainder is that ought to be covered by conventional food. The problem could well be that because you’re doing a mixed diet (and you’re perfectly entitled to do so), you may not be getting the correct amounts. Once all of this is done, you can make a few easy calculations either on a piece of paper or again on a website whereby you can see the total of the nutrients, micronutrients and macronutrients. You compare those results against what is recommended for people with your details, and then you add or reduce accordingly.
It’s entirely possible to avoid taking any supplements whatsoever. However, given that it’s a mixed diet and you don’t get the 100% of “something of everything in any way” (haha love it) you still need to find what’s left once you’ve taken your Huel and cover that through conventional food.
As someone who has been working with people who do have mild m.e, chronic fatigue and some forms of depression, I can tell you that the fact that you’re here discussing this issue with strangers is a positive sign that you may not have mild m.e (good news!). You may, however, have mood swings because of other factors like your work/home environment, emotional distress or merely stress about some things. You’re quite right, the journey is about being healthy and happy, so perhaps you need to invest a bit more in your happiness. I don’t mean that you should go out and buy 1207123 pairs of shoes haha! But maybe you have been neglecting what makes you happy and focused too much on what will potentially make you content in the future. I’m no expert myself on this topic as I struggle with depression every now and again, but I find that a combination of good sleep, healthy eating, frequent exercise, specific kinds of music and pursuing my hobbies help keep my energy levels high and mood on the positive side. But what works for me may not necessarily work for you, which is why everyone could benefit from learning more about themselves either by visiting their doctor or through self-awareness, or a combination of both. Good luck with your journey and keep us posted on your findings!