My 5 year old, female, Havanese dog, Sophie; seems to be non-productively trying to vomit. Along with that she also is having abdominal spasms, which leaves her shaking and her tail is constantly in between her legs. Her spasms last a while then she calms down, then they act up again. I am not sure if this is from the fact that she ate some grass. ( she has eaten grass before and has not had this problem ). Thank you for your help.