Not over her? and saw her kissing another guy?

I'm 17 she's 16 and we split almost a year ago and to make a long story short she didnt treat me right and i was harshly whipped like i would cry if she didnt call on time when she said because i would think she's cheating( i know its pathetic) and when she dumped me i was devistated because she was my 1st love and i treated her very well, too well actually. and it also hurt to know she started liking a guy 2 weeks after and i saw them at the movies together. Anyway just 5 months ago she tried to use me as a rebound like a fallback guy. And I didn't go for it and she got really pissed off and said she never wanted to see me again. And my older brother said she stepped into her own mess and i should man up (is he right?). but its still hard even though i lost my v-card 2 months after we split to a girl she knew and i had 7 times and also with 3 of her sisters friends that i met through a friend of mine and also going to prom with her school(my ex's). And just now i saw a photo of her kissing another guy and it kinda hit me? My brother would tweak if he saw me post this on answers since it shows i'm not being a man but i want this pain to be over. what should i do?