What Causes Delay In Period But Blood Flow During Urination?

My girlfriend is about 10 days late for her period. About 3 days ago she started to have a little blood when she peed. THis has continued but she says there is no blood on the tampon when she puts one in. She also is having to urinate alot more frequently but she acutally pees alot when she goes. Not sure what this means. We had sex about 4-5 days after her last period. She has been on the depo shot for about 6 months but did not get it this month. So she still should have been covered last month when we had sex. So its been 5 weeks since we had sex and about 2-3 weeks since she should have had her next shot. Is this a sign of pregnancy or just her body adjusting to not having the shot? She has always had her period normal while on the shot.