light brown/pinkish menstrual cycle for 5-6 days , pregnancy

hi, i was wondering if anyone could give me some advice as i am very confused, i have been on the pill now for 6 months and have regular periods, this month my period came on time but i noticed it was lighter than usual and brown/pinkish in colour and only lasted for around 5 days, i am also getting pregnancy symptoms such as tender breasts and nausea but took a hpt and it was negative, could i still be pregnant?

It really could be on or the another, pills can sometimes cause light, delayed or missed periods..Or you could have just tested to soon, I would wait another week or so and retest just to see, but the pills are suppose to prevent pregnancy, Are you consistent about taking them??