Period? Pregnancy?

August 27th-September 1st I had a full menstrual cycle. No unusual bleeding, severe cramps or any out of the ordinary feeling. However, on the week of Sep. 4-10 I have been having on and off nauseous spells. On September 14th, I had very light cramping and very light spotting (Out of the blue) that lasted an hour and was gone. I took a at home pregnancy test and saw a very faint line that appears to have went away over minutes of me taking a test, I proceeded to take another test this morning and it reads negative. What should I do? I visually saw 2 lines (1 being very faint) on one test & 1 line on the other.