Feeling jealous....

Okay, so I'm with someone, he's got 2 other kids with another women... she's only supposed to call about his kids,but she seems to call and talk about whatever other than his kids... when she callls when he's around me, he tells her right away ti call back tomorrow.... but wheb he's not around me, they are like on the phone for like 30mins... when he does answer her call around me, he talks really quiet with her, an walks away from me... idk what to do about that... /:- makes me feel she wants him back cause she calls him constantly... makes me mad....