What Causes Itchy Red Bumps On Legs?

Hi. I'm July. I'm 19. I get these red bumps or rashes on my legs, and sometimes they are itchy. I noticed that they only occur days before my period, and sometimes for the rest of my cycle. I've been experiencing this for years. I've done some research about it and discovered similar symptoms with Autoimmune Progesterone Dermatitis. Could this be it? Your answer would be a great help. Thank you!