I always suggest checking thyroid for thinning hair, but it sounds like you have that covered. Other symptoms of thyroid disfunction can be not being able to sleep well, or sleeping too much, or increase or decrease in blood pressure, it just depends if it is hypo or hyper. Additionally, with both hypo and hyper you can lose your hair, develop dry hair, and very dry skin or dry eyes. I only mention the other side effects, because it might be another clue before you get your test done.
Other hormones can cause hair loss, sometimes related to aging, but sounds to me like this is more than just a natural progression.
I’ve read that low and high iron can be a source of thinning hair, but the idea seems somewhat controversial, still probably good to check it. @Inspired_2write suggested Biotin, which is often suggested to help thicken hair, but if you haven’t changed your diet much, I don’t think it would explain suddenly starting to lose more hair, but it probably can’t hurt to try that supplement.
I read what you said above that you have been taking ibuprofen, and I googled and there is some mention of hair loss as extremely rare, but I really doubt the hair loss is related to ibuprofen. You could just switch to a different drug and test it, as long as you have no troubles taking a different drug.
Don’t let any doctors tell you it is the weather or that it is normal to shed hair. I can’t tell you how many times people and doctors have said that to me. Like I am 12 years old or have never noticed hair in my brush.