My period is 5 days late and I'm nauseous and have other pregnancy symptoms. Today I started lightly bleeding and cramping. Why is this happening?

Start with a test. If your period is 5 days late and you are having pregnancy symptoms, do a pregnancy test and, to know for sure, repeat it in 3-5 days if it is negative. This could be anything from the normal variation in cycle length, to an implantation bleed, to a threatened miscarriage. Hope this helps.