Losing handfuls of hair every time I run my fingers through it

I used to have such thick hair. I had my first child 3 years ago and after I had her my hair hasn’t stopped thinning. I just had my 2nd 4 months ago and the postpartum hair loss has hit me like a truck. I am losing handful after handful. My hair is so thin now. I don’t know what to do. Before I had my 2nd I had severe iron deficiency. So that could also play a part in it.

I was taking a womens vitamin, iron pill, and biotin. It made my body react terribly. I broke out on my face, all over my chest, on my back, even in my ears of acne.

I’m now taking a prenatal but nothing is working.

What can help?? I’m so desperate