Help a lady lol

I used a Venus razor 3 weeks ago (first time using women’s razor) that had that gel substance on it and after two days I noticed I was getting irritated down there and itchy. So I stopped using it and went back to my previous razor.

I’m very itchy on the side of my undies (you can see the skin is irritated from my scratching). It’s only on the sides and onto my thigh. I put lotion on the sides and it goes away for a little while then it gets itchy again. I had a pap done a month ago and that was clear, I’ve been with the same sexual partner for years now and I’ve never had any vag issues except 1 yeast infection (this does not feel like that). What could this be? Also what can I do to get rid of the darkness that’s there? It got super dark after having my second child. Also, discharge is healthy.