One would hope that the cause has been identified for your IDA, especially if you have clinical symptoms of anaemia, such as being tired all the time, or feeling out of breath etc. In essence, IDA is caused by;
1. Insufficient iron intake ( ruled out in your case if you have been taking supplementary iron)
2. Long term bleeding condition - Long or very heavy menstrual periods, bleeding fibroids in the uterus, a bleeding ulcer or colonic polyp. Long term blood loss is sometimes associated with long term use of non steroidal anti inflammatory drugs such as ibuprofen, or pain relief medication such as aspirin.
3. Hereditary dysfunction of the red blood cells, such as B- Thalassaemia, Sickle Cell anaemia, etc
The TIBC being normal really just illustrates that your body has the capacity to transport a sufficiency of iron, so the anaemia it isnt a metabolic or hereditary misfunction of transferrin or the liver where it is produced.
4. Absorbtion of Iron. The regulation and uptake of iron from the gut into the blood stream is still not fully understood - impaired gastic acid production can for instance reduce iron uptake, and certainly from what you have described to date I would think the problem might lie in this area.
I would be concerned, were I in your shoes, to establish the underlying reason for the anaemia as a priority, so that can be addressed , as soon as possible.