Hi,
Welcome to ehealthforum,
A tilted or retroverted uterus in not a contraindication for pregnancy. You can get pregnant while having tilted uterus, the position gets corrected on its own as pregnancy progresses and you cross 12 weeks of gestation. The symptoms that you describe suggest chances of pregnancy. Sometimes urine pregnancy tests can keep showing you false negative results during early pregnancy as the kits are calibrated ones, so unless the hormone levels in urine reach a certain level, they do not show positive results. If you suspect chances of pregnancy, you should consider visiting your doctor/gynecologist for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Drink plenty of water. Take adequate rest. Maintain healthy diet.
Take care.