PH Balance

How do I know if my PH balance is bad? I’m assuming your vagina would smell but is there anything else? I don’t really wash down there with soaps but sometimes I use body wash in between my thighs, and sometimes Vagisil will accidentally get inside, not on purpose but I’m wondering like is that super bad ? It doesn’t always happen.. but how do I know if the PH is bad & what could I do to fix my PH balance ?