Relationship advice

My so called “boyfriend” said to his brothers girlfreind they have a baby with each other and my boyfriend was carrying a stool over the baby his brother said “better not drop that otherwise you owe me a new baby” my boyfriend replied don’t worry I’m sure me and Vicky can make one. (his brothers girlfriend ) we’ve now gone to the park I’m sat there distant not talking.. he’s saying im over reacting I’m saying that’s flirting I’m not about that life I’m afraid 😂 am I over reacting cos I don’t feel like I am.