Your hCG of 26 against a cutoff of 10 does point to a very early pregnancy, even though your home urine test came back negative, since urine tests can lag a few days behind a blood hCG result. Mild back and lower abdomen pain is common this early as the uterus adjusts, but at this stage a doctor still needs to rule out miscarriage and ectopic pregnancy before confirming things are progressing normally.
Next Steps
Repeat a urine
pregnancy test and the blood hCG test in 48 hours to check the level is rising, then book an early pelvic ultrasound with your gynaecologist once it is higher. Since you are trying to conceive, ask your doctor about starting a folic acid supplement now.
Health Tips
Go to the hospital urgently if the pain suddenly worsens or shifts to one side, you get heavy bleeding, feel dizzy, or notice shoulder-tip pain.