What Causes Stomach Bloating,nausea And Headaches?

Hi,I have been experiencing bloating from about mid day (getting worse as the day progresses) and nausea all day for the past 3 weeks. I have also begun having headaches and a runny nose for the past 7 days. I am on microgynon 30 (pill) and have intentionally not had my periods for over a year as I get very sick. I took a pregnancy test and it came back negative. But following that I skipped one pill accidentally 2 weeks ago and 3 days later had light vaginal bleeding which lasted for 3 days (but my normal period has always lasted for 7days). I am sexually active and have been very consistent with the pill. Could this be related to anything other than pregnancy.