am I pregnant ?

I had sex with my boyfriend last week and I was under the influence of alcohol and I was smoking. He had came in me. Also on the weekend him and I were at it again. 
I have regular periods. Every Monday afternoon, and I have a light period with hardcore cramps. now the day before my period which is abnormal I have a browny-red discharge. Also abnormal.. Over the past week I have had back aches. Dizziness. Lack of eating. Headaches and well many things that's been classified as a pregnancy symptom. I'm thinking maybe it's all stress. The weather. And so on but I still haven't had a proper period sign and still getting discharge after 1 day. What could it be. ???