I really don't think that this is normal :(?

I have been seperated from my ex for almost two years... I have even fallen in love with a new guy who i have been with for a year :) the problem is i literally keep daydreaming and fantisizing about my ex. Out of the blue i would daydream me getting all dressed up looking gorgeous and talking to him.. Or i would fantasize about us being together and making love. I fantasize walking into a room full of him and his friends looking gorgeous and him drooling over me smh it is a bad habit. When i see him in person i get butterflies but i deny his request to get back together i even tell him no when he ask for my new phone number... But as soon as i go home i fantasize about him againi i get all dressed up look in the mirror and pretend i am talking to him.. It sounds so creepy but i promise i am normal lol i am so confused i just dont understand why i do this :( today i turned on music put on high heels walked up and down my hallway imagining he was there drooling over me with his friends.Why am i doing this?