My girlfriend is experiencing spotting since july 22. had last full period between july 1st and july 4th. sex once on july 19th, protected. pregnant?

If no period comes,: One can do a pregnancy test to find out. A urine pregnancy test done correctly gives a reliable result 3 weeks after sex (3 weeks after when conception might have happened) or 1 week after missing a regular period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and therefore lead to a repeat test.