Hello,
Welcome to ehealthforum and thanks for writing
Since you had unprotected intercourse possibility of pregnancy is high and the symptoms described by you as pink spotting could be indicative of that.Wait for few days and if the periods do not start consider doing a Urine test for pregnancy determination.You can also get a Blood hcg test done for pregnancy determination as it gives confirmatory results.
Kindly visit a Gynaecologist for evaluation.
Take care!