Nobody is using the toilet and it keeps making a sound like it is...?

Ya know how after you flush the toilet it makes a noise as it fills up.? well its 3 in the morning and Nobody but me is awake. Im 13 btw... and it keep making a noise like its refilling like, every 2 minutes... Its freaking me out D: and It sounds like somebody is turning on the shower... just when i think it stopped it makes the noise again... when its not making the noise I can hear a faint sounds... like somebody is slowly pouring alittle bit of water into it... It hasnt done this before.! whats happening .?! D;