I Have Always Had Odd Periods But For The Passed

I have always had odd periods but for the passed 3 months I had normal periods. This month was 2 days of brown and nothing at all, lower back pain and sore boobs also a bit of nausea throughout the day and still ongoing now over a week later I have no sign in getting my period. Could I be pregnant or can it be other signs I have one Fallopian tube removed from a tumour inside my tube two years ago. I had back pain and nausea but more severe.