2 year old shih tzu has repeatedly vomited

So my 2 year old pup seems to have also expanded in size lately and was wondering maybe they were preggo. We had tried getting her pregnant a couple months back. I was wondering if vomiting white foamy liquid was akin to human morning sickness? Is this something I should be concerned about or is it just something normal that happens from time to time? I think she ate a bit of spinach that fell aswell if this is something that may contribute to it.