Sorry you are going through this.
To echo others, things rich in Vit C help absorb iron whereas things high in tannins will deplete it. Always have your iron tablets with OJ, kiwi fruit, peppers or other Vit C rich foods. Look up food high in tannins and ideally cut down and don't take them with your iron meds. (tea, coffee, berries, certain nuts, red wine, dark choc etc)
If they have prescribed ferrous sulphate, then either you are still deficient or bleeding from somewhere. People will tell you that spatone and floradix are 'gentle' iron and better for you. That is because they both contain such little iron and are absolutely useless in correcting a deficiency. They are for maintenance only. This is a rough comparison to a daily, adult dose and the iron content:
Spatone 5mg
Ferroglobin 14mg
Over the counter multivitamin with iron 14mg
Floradix 15mg
Ferrous suphate 200mg tabs= 65mg- 195mg. Higher if you are on the 320mg ones.
I agree that iron bisglycinate is worth asking about. I assume its gastric issues you are having from your current meds? This can take time to settle if affected. Spirulina is a blue/green algae which is high in iron and you can buy tablets online or from health food stores. It is in no way to replace your prescribed iron meds, but can be used in conjunction with them. Wishing you all the best.