Is this a definite miscarriage my levels dropped from 93004 to 80000 in 48 hours i am 8 weeks?

Most probably no: If you have no pelvic/abdominal pains and no vaginal bleeding, you are very unlikely to be having a miscarriage. A pelvic sonogram will go a long way to reassure you. At this point in your pregnancy, blood betaHCG levels are not very accurate and not useful. Trust your body and see what happens. Consult your obstetrician and sonographer.