I'm going to fire a barrage of questions at you, but without knowing the full score we will find it hard to comment.
When you say Humulin, is it Humulin I? If it is then it's an intermediate acting insulin designed to be taken twice a day. Or is it another form of Humulin such as a 70/30 mix? They make several kinds of insulin so if you can tell us exactly which it is we can help you a bit better. Look on the packaging and tell us.
Are you on any other diabetic medications such as Metformin?
When do you test? Before/after meals and how long after? When are your readings showing 15 in relation to meals? What is your first morning test telling you (that is your level immediately upon rising)?
What is your daily diet like (I mean what exactly do you eat at each meal) and do you eat breakfast soon after rising? I ask because lots of people's blood sugar rises throughout the morning if they don't eat breakfast. This is called the "Dawn Phenomenon". See https://www.diabetes-support.org.uk/info/?page_id=143
I presume your diabetic nurse is the one at your GP's surgery? If so I'd be asking for a referral to the diabetic clinic locally which has proper DSNs and consultants.
I'm unversed in ferretin and Haemochromatosis, I am sorry. Hopefully someone else can help there.
Anyway, if you could answer the above it would make it easier for us to make suggestions
. Meantime so sorry you are feeling so poo... no one wants to feel like that, but do be assured that there is help out there and you could indeed feel better with the right treatment.