I don’t know if to get IUD

I started dating my bf over two months ago recently we have started being really sexual my bf likes it bare me too but I’m 17 and I suffer with really bad baby fever he knows but he keeps letting me look after his newborn nephew making it worse, im scared if I don’t get it done I will end up pregnant but I know I am not able at my age, I don’t know if I should go and get it tommorow or if I should leave it. What are the pros and cons of it.