Pregnancy after miscarriage?

I had a blighted ovum miscarriage on February 10 and completed it naturally. It's been over a month since then and I havent started my period yet. I know the doctor told me it could take 4 to 6 weeks to start my first period so it might just be that i need a little more time to get back on track. But im also wondering if i could be pregnant again already and how Id even know when to take a test since i have no expected period to base this off of. I'm experiencing sleep disturbances and vivid, frequent dreams and hot flashes which were the first symptoms i had with my last two pregnancies that drove me to take a test to begin with. Has anyone ever got pregnant before their next period after having a miscarriage? How did you know when to test and how far along you might be since there is no expectant period of base anything off of?