Re: earliest possible signs
Well for me, the earliest sign was a missed period. Even then I was sort of stunned because I didn't feel pregnant. My symptoms didn't kick in until around 7 or 8 weeks. By then I had known for about a month.
BUT, for some women it's sore/swollen breasts, nausea, constipation, bloating, extreme tiredness, cravings, increased or decreased appetite, food aversions, mild cramping, etc.
If you know when you should get period, then do a HPT around that time. There are early detection tests, but for some women it's more reliable to wait for the missed period. If you don't know when you're supposed to get your period but you feel pregnant, do a test now. If it's negative but you still feel pregnant, test again in a week. If it's still negative then go to the doctor and talk about the symptoms and possible diagnostic testing.
A pregnancy is not the only thing that can cause these symptoms. These symptoms are from the HORMONES associated with pregnancy, and wonky hormones from other problems, like polycystic ovaries, can cause odd symptoms as well.