Ive Been On The Pill For About 5 Months Now

Ive been on the pill for about 5 months now and for the past couple months I've noticed its hard for me to become wet despite being sexually aroused. Yet i still take part in sex which has now led me to having a very sore vagina and it feels like I'm internally swollen. Whats the cause of this and how can i help it? I'm only 18 this shouldn't be happening to me