Nellymag as others have said it’s advisable that you consult your GP. If your periods ceased 3 years ago this is classed as post menopausal bleeding and not a period. Hopefully something easily dealt with but it’s important to seek medical advice.
Postmenopausal bleeding Menopause is usually diagnosed in women over 45 who have not had a period for more than a year. Any bleeding from the vagina after this time needs to be checked by a GP
(I copied that from the NHS website. You’ll find more info there)