Should I use Monistat 7 externally only or should I use it internally as well?

I've been having some itching on the outside of my vagina area and when I had sex with my boyfriend it burned really bad. I'm thinking maybe I might have a yeast infection? The only problem I've noticed is the external itching though so I'm confused? Wouldn't my vulva and everything be itching too? I applied the monistat 7 externally because I bought it in the morning and it says to put it in at night but I'm not itching in there like that...

Can I just use it externally since its providing me relief and just leave it like that or should I put it in??