1. If you had been having a regular 28 days cycle, You may wait for a week more before doing the urine
pregnancy test on the first morning urine sample
Or else
You may do the blood test Serum
beta hCG. For this test you need not wait.
2. Did you take treatment like ovulation inducing medicines / hormone injections / follicular study scans this cycle??
3. Since you have been trying to conceive since the last 3 years, you may consult a Gynecologist / Fertility specialist for a detailed evaluation of yourself & your spouse.