Why does my vagina smell so bad?

My usually cleaning routine was just rinsing with water, but recently, I have been noticing a strange smell, almost chemical-like smell coming from my underwear. Sometimes, I can even smell it through my pants when I'm sitting normally. I started washing down there with soap and the smell only goes away for like an hour. It don't itch, and I don't have any weird discharge. What could be going on? And is there anything that could help?
By the way, I had a baby about 8 months ago, but I haven't noticed the smell until recently.
Also, I haven't had sex since before I had the baby. The only sexual activities I've done since having the baby is masturbation.