J Lo just laughed off rumors fiance A-Rod is cheating on her by saying, "It doesn’t matter. I know what the truth is."

Lopez was asked on Power 105.1's The Breakfast Club this morning about the claim by Jose Canseco last month that the baseballer is cheating on his bride-to-be.

She said, "I know who he is, he knows who I am. We’re just happy. We’re not gonna let other people come out and tell us what our relationship is; I know what our relationship is."

The couple announced their engagement March 9 and the very next day, Canseco Tweeted the allegation that Rodriguez had cheated: "He is cheating on her with my ex-wife Jessica poor girl she has no idea who he really is. I was there a few months back with her when he called her on her phone. Alex Rodriguez stop being a piece of s–t stop cheating on Jennifer Lopez."

His ex, Jessica, denied the claim: "Those false accusations Jose is making are not true. I have known Alex for many years and haven’t even seen him for over 5."

But Jose wouldn't back down -- he went on, on Twitter: "Alex show me now how much of a man you really are face the truth face a polygraph. Alex since you are a man’s man why don’t you contact me and we’ll talk about it face-to-face you know how to reach me."

But J Lo's moving forward with wedding plans, albeit, slowly. She told Elvis Duran on his radio show yesterday, "We’ve vaguely talked about, like, ‘Oh, when do you think?’ and things like that, but nothing is set in stone. We’re not there yet."

We hope more rumors don't come out in the meantime!