Can soft stool, feeling nauseas , and an upset stomach be caused by your period coming in a week?

Yes: Prior to getting your period, there is a marked increase in prostaglandins. These are neurotransmitters that are associated with the changes we experience before a period. They affect our muscles, our gastrointestinal tract, and our pain sensations as well. Very common (and very annoying!) to have these symptoms before a period. But yes, all of those are normal. Ibuprofen is best med to take.