Am I pregnant or could it be something else?

I am 26 and had a tubal ligation 2 1/2 yrs ago right after my daughter's birth but did not follow up6wks later to make sure procedure worked.I have a boyfriend  but we werent trying for a child. Now over the last week and a half I have been having nausea and vomiting, lower back pain, and breast tenderness. I know that some of that can also be pms symptoms. My period is due in a week so I don't think a Hpt would be able to show a positive result yet? How likely could it be that I could be pregnant again? Or could something else be causing me to feel this way?