Why do I feel threatened about her?

Okay so me and my boyfriend have been seeing eachother ever since we met which is about a month and we've been going out nearly two weeks now. But theres this girl Jade, my boyfriend was formally in love with her but she messed him about. She got with three different guys in the week he told her how he felt, they are bestfriends and they have known eachother years... I'm bestfriends with her, I have been for months before I knew my boyfriend Josh. But in a conversation the other night I asked 'have you ever heard anyone say anything bad about me?' and he said yes and explained that about a week into me and him seeing eachother, Jade had tried to kiss him and when he rejected her (apparently) she said: 'Hana isn't my bestfriend' (I'm Hana). And he then said 'she took it back the next day', I'm really worried he still has feelings for her.. The other day he mistakenly moved out of the way when she went to hug him and he went 'aw babe' and hugged her from behind :/ this made me feel jealous... He also asks her when shes out and puts the amount of kisses he puts to me on a text, I know it may sound silly but its really bugging me...