Itchy

Ok so ladies kind of embarrassing here

But i have a little problem so last year around December i got the deppo needle and was sexually active. Before i slept with the guy i got tested for sti's came back clear then after we split about 9mnths ago now i got tested again came back clear again but i have noticed since still getting the needle and now not being sexually active with anyone i have started to get an irritation on the top of my vagina i shave so just wondering if it just because the hair is starting to grow back or i have a skin irritation from the washing powder my mum uses.. its driving me insane i cant sleep