My Vagina hurts

I started birth control pills a month ago after my period. I did not see my boyfriend that whole month as he was away. I was due to have my period two days ago but instead I had a light yellowish discharge. It was itchy. And now, it hurts to have sex. Today I have a red spotty discharge. I know I am not pregnant coz I did not have sex the whole month. I had sex yesterday when my boyfriend returned. I think I may have a bacterial infection. What is wrong with me?