First of all, it's fine to ask questions like this on this site. They don't all have to be kid-related.
I had the same problem - lots of hair loss but also thinning and breakage. It wouldn't take a perm or color for years, it grew unevenly, and there was such a huge amount in the shower drain. I had some of those health issues including thyroid deficiency and menstrual & perimenopausal problems. Even with thyroid medication taken for years, on top of vitamins and supplements (big brand and also high-end stuff from the chiropractor), the hair loss didn't stop (in fact, it was worse).
I think if you can get some blood work to rule out things like a thyroid issue, that's good. My experience in this issue is that basic store-bought supplements, particularly if they are a single nutrient (such as Vitamin D) have little or no value. They simply aren't absorbed well, particularly in pill form, and they don't work by themselves anyway. Every vitamin, mineral, trace element etc. needs many other "partners" to function effectively. So the only people who benefit from all those bottles of pills are the people who sell them!
From my work with hairdressers, I can tell you there are some products that can help with dryness and conditioning, but what you are describing starts from inside the body. So nothing you apply to the hair after the fact is going to strengthen a hair shaft that's deficient. It's the same principle as applying skin creams or treatments for various topical problems (eczema, dryness, hives, acne, whatever) when the problem starts inside the body. You have to get to the cause which is some sort of imbalance.
I found that all my problems went away when I used cellular nutrition and got comprehensive nutrients into the individual cells. In all my training in this area, I've learned why it works. So now my hair is full and healthy, takes a color well, grows faster, falls out hardly at all (I rarely have to clean my brush or the shower drain), and I'm able to wear it long for the first time in many years. My hairdresser says she's never seen it so thick. I have fine hair (not coarse) and always have, but there is a lot of it. The side benefit is that I have gotten rid of other physical problems (allergies, for example) and I never ever get sick anymore. So nourishing the whole body in a systemic way is what food science is showing us all is a better way. It worked for me.
My husband also has a full head of hair. His is coarser hair, and always has been, but his is really full and healthy as well. All the guys who are losing their hair are pretty jealous of him!