some times periods can be delayed due to stress
, and some timed you might have less bleeding.
it is a normal varient. and your association of breast tenderness associated with your periods is termed as ANDI i.e abberation of normal development and involution. it is a benign condition of the breast.
i would advise you to consult a gynaecologist regarding the same who can prescribe you medicines for your symptoms.
and as of your pregnancy
doubt you can have urine pregnancy test done to re assure the negative status.
i hope i have answered your doubt
wishing you good health