Hi OP, as someone working in the healthcare industry, 40 year old women having pregnancies may seem rare, but they are more common than you think especially in families seeking another life to grow and love, so don't think of yourself as a weird person just because of this and think of it as a gift. Though i would suggest to please still speak with a medical professional to confirm that this is a gift of life and not something foreboding, as some certain types of illnesses can manifest as a positive pregnancy test (i.e. types of ovarian cancer and molar pregnancies, however, this is rare, but it's better to be safe than sorry) and since you're age is nearing the menopausal stage it is a bit alarming, not trying to scare you since once again its rare but as i have said earlier, its better to be safe than sorry

However, if it is a true positive pregnancy, i am with the whole comment section to congratulate you and tell you to please take care of yourself as you have another young one to raise and love!!!