Help please

I am 21 weeks now. I am having a pleasant pregnancy so far except that my lower back gets strained easily.. And from about week i feel itchy on my labia. Got it checked by obgyn they ruled out yeast infection. She asked me to use monistat. It keeps coming back alternate days. Please lemme know if you know anything that could help this and my back pain. I use snoogle n sleep on side. Thank you