I'm far from an expert BTW. What was your Hb reading? Haemoglobin is your iron level, whereas ferritin are your iron stores. Generally if your stores are low, then your Hb will also soon drop- but you can have low ferritin and a normal Hb.
For context, my ferritin was 2 and Hb 96. I was getting short of breath, dizziness, constant UTI's, fatigue and unusual food cravings- all signs of anaemia.
IF the GP thought your levels were too low, they should have prescribed iron supplements which are many times higher than over the counter ones, or advised an over the counter supplement. Over the counter are for maintenance only- not to correct an actual deficiency. Unlike Vit C supplements where any excess is urinated out, iron doesn't excrete and metabolise in the same way, but builds up. This is why taking iron supplements unnecessarily can be dangerous.
I'm always amazed by people mentioning spatone in reference to anaemia/low iron and don't think they realise how little elemental iron is actual in a daily dose ( 1x sachet).
Spatone- 5mg (36% daily iron)
Over the counter iron pills (often with multivitamins) 14mg (100% daily iron)
Prescribed iron (ferrous fumurate 210mg) which is equivalent to 70mg- 210mg of elemental iron (up to 15x a daily dose)
IF your Hb is low and they do recommend prescribed iron, note that it takes 3mths for red blood cells to replicate- so even with meds, increasing meat in diet, reducing tannins, its not a quick fix. I started feeling better after a month- but my levels were very low.
Did your GP do any other blood tests? Thyroid, hormones, Vit D? What do you mean by feeling rough? Certainly don't start taking iron supplements without medical advice, but go back if unsure or still feeling unwell.