Hi, and thanks for your medical question on eHealth forum!
Jan 25th was the 15th day of your cycle, and hence that could have been ovulation bleed. Normally, in this case, sex on Feb 5th and 7th cannot make you pregnant. However, cycles are known to behave differently at times, and you could have ovulated later, or had sex earlier too.
If urine test is negative, then go for a blood pregnancy test. A blood HCG estimation test would be more reliable. If the test is negative then you are not pregnant. If it is borderline, repeat after 48 hours to see if the levels are rising. Rising levels indicate pregnancy.
If this too is negative then other causes of delayed or missed periods will have to be looked at such as ectopics (can give negative urine/HCG tests), stress whether emotional or physical, hypothyroidism, polycystic disease of the ovary, pituitary tumors secreting prolactin, anemia and poor diet, hormonal imbalance, unexplained or sudden weight gain or weight loss. You will need to consult a gynecologist for this. Hope this helps. Take care!