It is hard to know if the symptoms are cardiac or not. They could be due to the low hemoglobin or could be due to your heart or gastrointestinal track. You need to be evaluated by your doctor.
Mine hb one stage had fallen to 7.8. They didn't give me anything. Few months later, the GI doc gave me a big bag of iron infusion.
Apart from low hb, why and how it happened? It is still in the mystery. I have wpw and a pacemaker. When I notice I have quite a bit of irregular beats, I went to ER and my HB was 12.5. Six months check up, the cardio said I got A-Fib. He put me on various of drugs (medication). My hb was starting to fall from there. Seems like my body unable to produce or maintain the iron. GI doc went through upper and lower endoscopies. It's all normal. OK, the cardio blamed all to my low HB. Now my HB is fixed (not on cardiac drugs). My heart never behave like before...... He still thought it is nothing to do with him and pushed me to the heamotologist. The Heamo said my blood tests all normal. See Gynae. Gynae said I'm in perimenopause, fix your heart first. I was passing like a ball in the middle of no way.