Heavy periods, confusing blood test

Hi, I have had very heavy, clotty periods for 13 years. I had a blood test last week which showed my haemoglobin was well within the normal range. However my ferritin levels weren't checked. I have so many symptoms of iron deficiency and quite frankly I don't see how my iron levels wouldn't be low since I lose so much blood every month and I rarely eat red meat and mostly just have reformed breaded chicken rubbish! I did start taking 14mg ferrous fumerate tablets last year but I've been a bit patchy taking them in recent months. Although I did have two the weekend before the blood test, so maybe that skewed the haemoglobin levels? Has anyone else had normal haemoglobin levels but still been iron deficient? I don't know whether to go back to the GP and request another blood test, this time specifically for ferritin. I'm afraid of being brushed off.

So I found results from a blood test I had done three years ago, and I seem to have been at the low end for the following:

Hb 129 g/L.Quoted range is 120-160
MCV 85.4 fl range 85-105
MCH 27.9 pg range 27-32
MCHC 326 g/L range 320-360

My RBC was at the high end: 4.65 range 3.8-4.8