AF Due today- didn't come

I'm 10 DPO, AF was due today but didn't come. I had cramping last week and spotting last night. Could that have been implantation bleeding? Took a FR test on Friday and BFN. Should I retest and when? I've been nauseous and lightheaded for 2 days. I'm dreading getting another BFN. Had a miscarriage almost a year ago to date; and husband and I have been trying for 2 years in October. Thoughts?!