Try getting closer to the subject, either physically or through the use of extention tubes. depth of field is dependent not only upon the aperture but also the distance the film/sensor plane is to the subject.
Depth of field is also dependent upon the physical size of the film plane or sensor; the smaller tje format the greater the dof at any given aperture and distance.
You may also find that getting the desired dof and correct exposure may require a lower iso setting/film.
You can blur the background digitally if your equipment
does not allow you to do it in camera. the smaller than full frame sensors, vis a vis 35mm, are really a bear to deal with when you want to use a selective focus technique.