4 months after having my twins i'm losing hundreds of strands of hair per day. my hair is thinning. is this normal? will it stop? is it hormones?

Expected : This is called telogen effluvium and is a normal process after giving birth. It last 6 months to a year. It's worth having you thyroid checked but usually it's just something that happens to some.

Sequencing issue: As Dr. Livingston said, this happens to some & will revert to normal later. The normal person sheds/starts 25-50 hairs/day. In a variety of stressful events the body goes into a shed it all phase for several months before it resets to normal. It is dramatic and worrisome, but it is not permanent and not a sign you did something wrong or need to have special rx. Your doc can elaborate further.