My boyfriend’s ex-wife is back, and pregnant

My boyfriend had separated from his ex-wife for 2 months when we met. After dating him for 5 months, he found out that his ex-wife is pregnant with his child. It didn’t end our relationship and because I love him, I let him be a father to his child. Now, the baby is 3 months old and my boyfriend has been spending more time with them. I think he’s falling back in love with his ex but every time I ask him, he would say he’s only there for their child. Should I trust him or should I just end our relationship and save myself from getting hurt?