Should I get stressed about pregnancy?

Hi, since 8 months of taking milvane birth control pills at the very beginning for a period of 2 months I had abundant sting / bleeding for a period all this time. Everything returned to normal, so too reassured me my gynecologist that it is normal when taking the first birth control pills. Today I'm at 8 opakovwniu at 7 tablet, islanded with me for 2 days staining, a little hurt my lower abdomen. I take the tablets regularly, I have never left a single one I always take at the same time. During the break between 7 and 8 packs I took an antibiotic, it may also have had an effect on those sting or stress that has accompanied me over the last days. I also smoke cigarettes I know that they also affect taking tablets. Please advice if I have to stress whether it is pregnancy or I have health problems?