Theres this girl at my school n she talks about me behind my back?

hey im mandy ...well first theres this girl at my school her name is anna n she one grade higher than me n i have to admit she one of the prettiest girls in the grade... shes popular n shes kinda the ring leader of her group and well anna has been goin out with this guy in my grade which makes no sense cuzz hes one year younger his name is nick but... a few months ago they broke up then a few weeks after the break up nick started talking to me n he told me he liked me n he was really sweet n nice and he asked me out n i said yes... so before we started going out i use to talk to anna n we were sorta friends but once i started dating her ex she wouldnt talk to me n soon i started hearing things that were not true about me that she was telling ppl and the ppl would come up and ask me ... n i would be like no none of thats true... soo a few weeks ped n he broke up with me .... i still liked him n he told me he still liked me... and he still calls me every night which would make no sense.. but then shortly after the break up ... my friend mary whose is sorta close to nick told me that the other night he txted her i need some advice who should i ask out anna or mandy ?? and at the time anna was on to some other guy and the two were dating... and soo mary tried telling him that anna was dating some one else n he said i no that ... thats why im talking her into breaking up with her... well when mary told me what he said i was tottally hart broke bc i thought he still liked me n stuff... n so that night he called me n he started asking me questions liked wat would you say if i were to ask you out again n i said yes n then i asked him rate from 1 to 5 how much do u like me n he said 5.... but that didnt make sense bc i thought that he liked anna .... so i asked him if he still likes her n he said noooo... so i was like ok n im still a lil confused... i still love him n i cant get over it.. but he still has been calling me until just two days ago n i was wondering why but i called him last night n he said why are u telling ppl that we are going back out again n ... was like i didnt and nick was like well how come anna told me you messaged her and was like haha im going back out with nick and theres nothin you can do about it *****... and then i told him none of thats true n he goes y did she tell me that then n i go i dont now cuz i hate her... so today i was i face book n she sent me a message y do you hate me?? n i was like maybe thats cuzz uve been talking **** about me behind my back and some of it not even true... and she still hasnt responded but i need some good come backs and i need some advice on what to do cuz im always see her in that halls n also i need to now what i shood do about nick....please some one help!!!