I'm due for my period on Tuesday, but I took a test this morning and got a very faint positive

I'm due for my period on Tuesday, but I took a test this morning and got a very faint positive! I came out of the bathroom, looked at my husband, and said, "Happy Father's Day, you're going to be a dad again!" Best Father's Day present I could have given him! (We tried for four months to conceive baby number 2)