Lower abdominal pain can have many causes, such as gas, constipation, urinary infection, menstrual issues (in women), or intestinal infection. For mild pain, try drinking plenty of fluids, eating light meals, and avoiding spicy or heavy foods. A mild antispasmodic or paracetamol may help if suitable for you. However, consult a doctor for proper examination and tests to identify the exact cause and receive appropriate treatment.

An evening fever of around 100°F with one-sided pain from the back to the knee may be due to a viral infection causing body aches, muscle inflammation, or sometimes nerve-related pain such as sciatica that becomes more noticeable during fever. For relief, you can take Paracetamol, rest well, and stay well hydrated. If the symptoms persist beyond 3-4 days, become severe, or are associated with weakness, numbness, or difficulty walking, it is important to consult a doctor. Your doctor may advise basic investigations such as blood tests (to rule out infections) and, if needed, imaging like an X-ray or MRI to check for nerve or spine-related causes, and then guide further treatment accordingly.