Losing hair? Shortening of hair?

Hey ladies so I’m only 24 and my hair has been getting shorter :/ I’ve always struggled with growing my hair out throughout middle and high school. Finally in college, I was able to grow it out pretty long past my boobs. I was treating it really well. I still do so I’m confused as I was looking through old pictures why my hair was so much longer back in college just a few yeas ago compared to now. I get it highlighted maybe once every 2 or 3 years and never bring any heat to it. I have curly fine hair. Help! Any advice? I’m healthy. Are there any supplements I can take that will be a life changer?