how do i trust again?

My boyfriend had an emotional affair with a much younger girl he works with. We had been having relationships issues since having our son 2 yes ago and had pretty much became roommates nothing more we work opposite schedules and just became distant which just caused more issues like resentment and feeling alone. He became close to this girl because they saw each other lots and have lots in common so started texting here and there then it became more. They say it was never like a sexual relationship neither of them see the other like that but each became that person they could talk to and they said they loved each other but more of a brother sister kind of love not an IN love kind of way. However I've been cheated on physically and emotionally before by my ex and have always been told I'm worthless in my life was bullied and so on so I have always had low self esteem now this kind of put me over the edge my bf says he loves me but isn't sure he's IN love with me anymore but wants to renew that love we once had.. We've talked about tons of issues since this happened (found out end of Nov) and I've been trying but since they still work together (have to talk and see each other and changing jobs isn't an option) I'm finding it hard to like deal with it feel like every time they talk takes me back to what happened. How do I learn to deal with this all I want to move forward and heal us he told her they can't like flirt anymore or talk like that like ended it but I always have that small piece of doubt mainly because of how many times my ex screwed me over just scared they'll cross that line again.. We have a son and both want this to work out but scared its too late that hell never be IN love with me again and I won't be able to get past this.. help!!