Relapse of symptoms 4 weeks after infusion. What does this mean?

Doctors and going to the emergency have been worse than useless, doing more harm like needing to suffer withdrawal symptoms from unnecessary antidepressants.

More than a month ago ferritin was tested to be 7 and haemoglobin 127 g/l.

Got 500 ml of monofer infusion. 2-3rd week I saw improvement, until my period came on June 6.

June 8 my face was really pale. Debilitating head rushes come back as if I was back to prior iron infusion. Feeling like my hand does not belong to me type debilitating and severe concern about long term effects on my brain.

June 9 face got color back. But head rushes still shit, have to walk like a pretzel and take 5 minutes of shaking my legs and very slowly getting up to maybe mitigate some of it.

June 10 very light bleeding, probably the lightest period of my life and ends here. Head rushes starting to get a little better but now an episode of rapid heart rate wakes me up at night.

June 11 to now, progressively worse heart rate. Back to heart jumping out of my chest after taking the stairs. Lightheadness, faint, everything is fuzzy, confusing and terrifying. Sometimes whilst resting my heart rate increases "out of nowhere".

I am going to take a blood test in a day. Is this a ferritin issue or is something else acting up? Would my ferritin really drop this fast? What else should I test? I have been using cronometer since 1 month ago to get all my micros (b vitamins, magnesium, copper, etc) in range as they have been on the low range, but not deficient as was ferritin.

Something was going on with me since 7 years ago, as I remember waking up breathless and with rapid heart beat, but this was brushed off by everyone as anxiety and just needing to exercise more. It only started to be debilitating bad, thinking I will genuinely die, 2 months ago. It feels like I am going to die again.