My boyfriend talked about a future with someone else

I went through my boyfriends texts and he discussed the potential of being with another girl in the future

My boyfriend used to be really into this one girl before me. He pursued her for over a year before she stopped talking to him and then I came into the picture about a month later.

Not long after that, they started talking everyday, and they talk everyday until now and it's been over a year. I'm aware that she is interested in him, but she isn't ready to date anyone yet according to her.

When I went through his phone, I found messages of him saying he asked her out even through all of her troubles, and that ''maybe in the future'' they could be together.

What does this mean for my relationship? I don't know what to do.