Itching down there

It seem like sometimes I itch down there when I am on my period or after my period goes off or before my period comes on. I am sexually active but this problem started way before I started having sex with my boyfriend. When I do have this problem it’s been a yeast infection. But I did have this problem last month it did go away after a while. I also itch in my butt area too. I really don’t itch inside my vagina it’s like that little area.(picture shown below). But why does this happen sometimes around that time? Does this happen to anyone else? Oh