I confess.. That I keep up with his ex..

Yes, I became that "girl" that stalks his ex girlfriend. 
Am with someone and it's about to be a year, within the time that he's been with me his life has changed sooooo much ! Everyone tells me that I've changed him into a man and that we have a bright future. 
I've always been their for him and I never let him down. 
His past relationship with this girl lasted for four years !! So yea... I get discourage and scared that she might want to look for him or he might miss her I mean it was a long time. 
People tell me that his relationship with her was nothing but fights and that she was slutty. Looking at her social media I believe it because she's chubby and has big boobbbbbsss !! And they are always popping out in every single picture !!! 
And yea that makes me uncomfortable..... 
It's been a week since I've "lepta up with her" and I feel a lot better ! Like am only in competition with my self no one else.. Not saying am better than any one.. I'd never do that but I want different things. I want to build  a home, and a business with this man. I love my relationship with me.. It sucks it took this long and I hope I stick to my promise to my self. 
Egh am I the only one that's ever gone thru that ? And what are your thoughts on keeping positive?