The singer talked about this with TIME Magazine -- where she opened up about her getting used to being alone ... this after being single for upwards of five years, and her coming to terms with the fact she might have to be a parent all by her lonesome.

As a result of that possibility ... SG admits she was ready to bring a kid into her life, even if she didn't have a man to do it with. She even had a time frame for this ... age 35.

She says, "I was alone for five years, and I got really used to it. A lot of people are afraid of being alone and I probably tortured myself in my head for like two years being alone, and then I kind of accepted it. Then I came up with my plan, which was I was going to adopt at 35 if I had not met anyone."

Then, along came Benny, and now Selena -- who's turning 32 this summer -- is re-thinking things ... including whether she'll have kids with him.

We know he wants children ... he made that really clear while on 'Stern.'

Selena acknowledged the fact Benny is so open and that he wears his heart on his sleeve -- noting she's not really like that herself, saying ... "I know what people can do to people I love. My own fans, who I adore and feel like have shaped who I am, will say the most hurtful things to me about how I live my life."

She adds, "But he has the strength in him that none of that noise fazes him. It’s really impressive, and I just cherish every moment with him."

In terms of where things are gonna go from here with BB, Selena says time will tell ... but does say this about him, "I don’t know what the future holds, but I do know that he’s not going anywhere any time soon."