Hi, can relate to what you are going through. Last three months I've been struggling to keep my hair. I don't ever realized how this happened. I've never gotten 300 or 500 hairs per shower or something but I developed crown thinning, small bald patch and thinning patches on left and right side. I gradually developed fungal infection and seborrheic dermatitis.
First I noticed increased shedding was when I watched a video about hair and it said if you get more than 5 hairs from running fingers through your hair you are experiencing hair loss. I did and I got 7-8 hairs. I did it second time, third and again 7-8 hairs. I could not believe I was losing my hair. I decided to style my hair with my fingers and I got up to 40-50 hairs. I used yo have 5-6 before when I did this. I noticed that my head is itching and my hair is greasy even after a wash. Before I used to remove all of my greasiness when I just washed. The itching started getting worse until my scalp became painfully inflamed. I strated tar shampoo and rosemary shampoo and they did nothing. Luckily the shedding stopped and I again styled my hair with two to five hairs. I developed severe dandruff too. I noticed that I shed miniaturized hairs but I used to tell me that they aren't from the scalp. As I said I couldn't believe. When I noticed my bald patch on the left temple I got very self conscious about it. The only things that helped me are: Vinegar, wooden brush and stress relief. Nothing else. I bought a wooden brush recently. Massaging your scalp with a wooden brush really helps me strengthen my hair and reduced my inching and inflammation. I am doing every day relaxation for 5-10 minutes. It really reduces hair fall.
How is your current shedding? Do a pull test. How much hairs you get in your hand. On your pillow case?
My current shedding is 4-5 hairs on the pillow, 0-4 hairs when I take off my hair tie and 10-15 in the shower. There are alot more because the rest get stuck in my hair because it's curly and messy but that's what i see. Before the vinegar and wooden brush it was like 25-30 in the shower, 8-10 on my pillow case, many of them miniaturized, and 5-8 when I take off my hair tie. Today I still shed miniaturized hairs, maybe because I skipped certain areas the first two times when I did massage with a wooden brush. I hope it stops. Despite losing a bit of density and having some miniaturazation, my hair still appears pretty thick. I can't imagine how thick it would be if my scalp was healthy. This disease is being cured very slowly. I used to have insanely greasy hair, severe dandruff and painful to touch scalp and now I have everything in moderate amounts. The bald patch in my left temple is filling with hairs but i don't know if you the other places are improving.
Your hair loss is probably triggered by the thyroid medication you are taking. My advice is getting your vitamin levels checked. You may have some nutritional deficiency. Remember that the lab test ranges are very wide and your thyroid hormones levels and vitamins should be in the middle or above the middle. They shouldn't be lower than the average level or barely in normal range.
Quit minoxidil and finasteride. Especially finasteride. You are taking it for no reason. These medications are doing nothing for you. Doesn't matter if topical or oral. Go buy a wooden brush it's very cheap. You can try relaxation to reduce stress and vinegar too.