mschristine
Sorry to hear about your issue with thinning at the crown. Meications, stress, hormones (as you mentioned switching BC pills), anemia (I'm anemic, but not due to iron), and lots of other things can cause thinning.
Seems like the crown, nape, and edges are the first to suffer when it comes to thinning that is due to something going on in the body. Stress increases cortisol which leads to weight gain, increased cholesterol in the blood, and other issues. Hopefully, the thinning will subside quickly as your body adjusts. Try to pay extra attention to the crown area by massaging and being careful with the hair there. HTH! P.S. My mom and future MIL both have significant thinning in the crown due to blood pressure meds.
FMIL actually is shiny bald there and has to wear wigs...my mom is very thin there but she doesn't pay me any attention when I suggest hair and scalp remedies! I know the blood pressure meds are the culprit, after I gave birth to my daughter and was out on them for 6 months, my hair shed more and was thinner too. I was also on a chemotherapy med (not for cancer, but for adjunct treatment to boost bone marrow) once and it caused more shedding, but the side effects were too much and it did more harm than good. I hope your shedding subsides soon!
Another treatment is the juice of onions applied to the thinning or heavily shedding area before washing hair. Leave it on 1 hour then wash it out. Onions contain sulfur and we all know sulfur grows some hair! Lemon juice and water rinsed over the hands or scalp will get rid of the onion smell if the shampoo does not. Lemon juice applied to cutting boards after chopping onions will take away the smell and it works on skin too.