Am i overreacting?

my husband & i have been married for 3 years now. We have a 10 month baby.

He has a 6 year old with amother woman.

Ever since they broke up (2015) she's always begged him. We live in California & his parents live in Mexico. Each year he goes to Mexico & each time he goes, she's there. i've always tried to keep my cool & trust him. But he's going again to visit his parents ( they can't come to U.S because they're undocumented) & it's gonna be one of his brother's birthday. They're gonna throw a party & she's obviously going to be there since she & his brother get along pretty well. The thing is, everytime she's drunk, she always calls my husband. 😒 She doesn't have his new number , but whenever he calls his mom & she's there, she tries to speak to him. She doesn't even talk to him about their son , she just tries to make a whole ass other convo. Anywho. He's going to Mexico next weekend & even though i'm trying to pretend like i'm okay with it , i really ain't. I'm in process of getting my residence , so i can't travel to Mexico with him. I know this woman will get drunk( she's a drinker ) & he will drink too. So idk... I'm just over thinking i guess...

Sorry i forgot to add, he says he's done with her & that the only thing that keeps them close is their son. i know i know. i guess i'm just a little insecure.