What Causes Nausea And Vomiting While Tubes Are Tied?

I am 39 and experiencing nausea similar to when I was pregnant. I just had my cycle which as not normal. The first day was quite heavy and I spotted for 4 days. My normal cycle is heavy first 3 to 4 days and lasts seven full days. I had my tubes tied after my youngest daughter was born 16 years ago. I have not been able to eat and the thought of certain foods, makes me want to throw up. Could this just be nerves?