I assume from your question that the stroke left you handicapped and confined to a wheelchair because of leg weakness. Under these circumstances, you should not attempt to transfer from wheelchair to toilet without help. As time passes and your rehabilitation continues, your strength may improve. But, for now, you need help in transferring. Be patient and work hard with your health professionals to regain your independence.
Patients often have low blood pressure after a stroke.
In my experience, however, this usually does not hamper activity or recovery. Don't try to do more than you're capable of accomplishing. A fall could result in a serious injury that would prolong your convalescence. You don't need that.