Hi dear, I have gone through your question and understand your concerns. Not taking depo provera shot on time can lead to decreased contraceptive efficacy of this drug and pregnancy can occur. However, if the urine pregnancy test is negative, then the pregnancy is ruled out. Nausea, headache, lethargy and weakness can be present in other medical illness like myalgia or viral infection, and you should therefore consult a physician and get properly examined, investigated and treated accordingly. Hope you found the answer helpful. Regards Dr Deepti Verma