Hi 

sorry to hear you have to go for a colposcopy. Have you had a letter through from your smear as well? If not you will prob receive one soon, which will state if you're HPV positive etc.

usually (well in my experience) if they ask for you to go for a colposcopy they have identified some abnormal cells on your cervix. Once they look at your cervix they will descide best treatment. Sometimes thu leave the cells and monitor them as they go back to mornal on their own, or other times they remove them. Mine were severe Pre cancerous  cells so they decided to remove mine under local anaesthetic, as higher risk of them developing into cancer. Since then I've had clear smears and all ok.

id maybe chase up your smear results letter as that might give you bit more information. Try not to worry to much, abnormal bleeding can have lots of causes and not necessarily the worst case, but it's good they are checking you out. 
I've got mine tomorrow as had similar symptoms as you and bleeding after sex so bit nervous x