What Causes Light Pink And Brown Color Spotting During Menstruation?

the day my period was due i started spotting its been very light pink and light brown not enought to wear pad or tampon its been 6days it stoped but day 5 i went to the er and my hcg levels were zero nd the ultersound showed nothing could i still be pregnant? i do pee more like every hour and i was feeling nauses on and off a week ago, once in awhile smells or taste will make me feel that way still, its been about 3 weeks sence my boyfriend and i have done anything, im so confused and scared it might be somthin worst then i exspect... plz help