I'm a bit confused as the first day of my last period was 19th feb, and I bled till the 23rd, so I isn't had a period for 36 days now, and I'm normally very regular, my boobs are very sore, and I am a little more sleepy than usual, but I do bleed when I have sex, and that's it. What does this mean? Why is my period not normal and only making an appearance when I have sex?

Have you tried a pregnancy test? Bleeding after sex can be due to irritation, it could be that you are pregnant and the bleeding is from the increase blood volume in the area.

Take a pregnancy test at home or see your doctor or midwife and have one done. If you are not pregnant, they will either have you wait until your next period would be due and see what happens or they may want to do some more checking to see why you are having bleeding after intercourse.