Yes, you can sleep in whatever way is more comfortable for you. Moreover, during the first months of pregnancy, your stomach has not grown bigger yet.
Nonetheless, as the pregnancy progresses, the most recommendable is to sleep on your side.
Bachelor's Degree in Biotechnology from the Technical University of Valencia (UPV). Biotechnology Degree from the National University of Ireland en Galway (NUIG) and embryologist specializing in Assisted Reproduction, with a Master's Degree in Biotechnology of Human Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI)