What Causes Spotting?

im 30 years old, started my periods at 11. Ive always been regular (give or take a few days) Ive got the exact same pains this month but ive got black stains in my sanitary towel and on the toilet roll instead of the usual red!! Ive got a 9 year old daughter and had the same partner ever since. Im worried and harldy have the time to visit doctors due to work please help. Marie