dissertation!!!

Hi I am a history student coming up to my third year. I am worried i have left everything too late for my dissertation. I really need some advice on what to do. i think i want to change my idea. is it too late? i haven't really done any research on my topic i just chose it because i think looking at topics of history that dont get discussed a lot i want to do something related to lgbtq community and class but now i think i have made things difficult on myself. i havent done anything yet. have i ruined everything by leaving it so late i am so worried can someone help please.