What Causes Bruising Inside Vagina?

Hi. I am 23 years old and have had the same partner for 3 years now. For the last month or two, I have been feeling bruised inside my vagina after sex. I only feel this when we attempt to have sex a day after the sex that has caused the bruise feeling inside. We used to be able to have sex multiple times without this uncomfortable feeling. Also, often after sex, I will wipe and find a clear discharge with a bit of blood in it. Please help me figure out what is happening.