How early can you catch on that you're pregnant? What are are signs and symptoms to look out for? Whats the earliest sign to notice?

Hi po. ask ko lang po kasi June 10, July 10 po ang period ko then nabago sya ng July 31- 1st week ng august. Last contact po is after mens, Nag PT po ako netong august 20, negative naman po. August 25, nagtaka lang po ako kasi dinugo ako na parang mens talaga, wala lang siyang clot at 2days lang po. 29&30 spotting po. Kelan po ako kaya dapat magkaroon?