It's understandable to have concerns about potential pregnancy. Since your girlfriend's period arrived on January 16 and was relatively normal, it’s likely she is not pregnant. The negative pregnancy tests further support this, but it's crucial to note that test results can vary based on timing and hormone levels. The back pain she experiences may be a regular premenstrual symptom. For reassurance, consider having her consult a gynecologist, who can offer personalized guidance and may perform a more sensitive pregnancy test if needed. 

The presence of jelly-like yellow granules in your ejaculate can be due to various factors, including dietary habits and hydration levels. It's good to hear you have no pain or burning sensations. Fatigue and sleep issues may relate to your lifestyle or nutritional intake. Consider incorporating a balanced diet rich in fruits, vegetables, lean proteins, and staying hydrated. Regular exercise and good sleep hygiene can also improve your energy and rest. However, it's essential to consult a urologist for a thorough evaluation and personalized guidance. 

Testicular discomfort can arise from various factors, including inflammation of the epididymis. Symptoms often include swelling, tenderness, or heaviness in the affected area. This condition may be linked to infections, physical injury, or other underlying issues. It's essential to stay hydrated, avoid strenuous activities, and apply cold compresses to alleviate discomfort. However, seeking medical attention is crucial for accurate diagnosis and appropriate treatment, as urologist can recommend the best course of action.

It's understandable to be concerned about your missed period. Various factors, including hormonal changes, stress, or the influence of emergency contraception can cause menstrual irregularities. A negative home pregnancy test is reassuring, but since your period has not returned, it may be beneficial to consult a gynecologist. They can provide insights, perform necessary evaluations, and discuss possible solutions. 

Based on your detailed information, it is very unlikely that you are pregnant, especially since you have had regular menstrual cycles and negative pregnancy tests. The ultrasound conducted 13 weeks after the event further supports this. Cryptic pregnancies are rare and typically present with symptoms like missed periods, but you have had normal bleeding. If you remain concerned, it's reasonable to consult a gynecologist  to address any lingering worries.