stress pains

I never posted on here before but i would appreciate some help please 😔 I'm having issues with my boyfriend the father of my child. He has this "friend" that he has became close to. they say they are just friends but have cuddle and talked about cuddling more when they see each other again. they say I love you, want to hold hands, lay on one another, and whenever he has free time he cant wait to see her. i told him not to cuddle or be alone with her and reading through his messages I learned he lied to me. they have only known each other for less than a month. its causing serious problems with us and im 26 weeks pregnant and the stress is causing me pain. I dont know how to control it or stop from feeling so broken. please if anyone has advice I need it right now.