experience with chemical???

So according to glow today starts my fertile week... I had a chemical pregnancy( threatened miscarriage) on the 16th. My obgyn said I could get pregnant immediately or it could take a few cycles... I've never used opk do the dollar store ones work? Has anyone gotten pregnant quickly or did it take long? This was my first pregnancy and I was so so so excited and now I just don't know where to begin. Any help would be great!