What am I doing wrong :) Iron Supplement Question

I (22F) had a ferritin of 6 in October 2024. My iron saturation was 8%, MCH 26.2. Other labs besides ferritin have improved. I've been getting my ferritin tested a few times a year, but it keeps going up a little and then dropping back down. I can't seem to get it higher than 25. My ferritin from labs taken last week was 24.

I take one Ferrous Gluconate 324 mg pill every other day with a 250 mg vitamin C tablet. The ferrous gluconate pills are coated, and I think the brand is Perrigo. Usually I'll drink a little coffee two hours later.

Symptoms: I feel so exhausted every day. My chest used to feel heavy when I would lie down, but that has improved. When the ferritin was really low, I would also get heart palpitations that would last 30 minutes or longer, but those have stopped.

My question is: Am I taking the wrong kind of iron supplement, and could anyone recommend something that might work better? I just can't risk constipation from the iron supplements.