I can answer some of this....I had headaches and very tired, which are for me typical PMS signs. So I guess, yes, PMS and early pregnancy symptoms can be similar. I know many women have no pregnancy symptoms until 5 or 6 weeks, but I get them about 1 week before period would normally be due. As for Dr. test, yes a blood test will pick up HCG before a urine test (at least I am pretty certain it does). First response can usually be used with pretty good accuracy about 4 days before period is due (first urine of the morning works best) A false negative is not uncommon, as different women will have different HCG levels at that time, but a positive usually means a positive.
I hope I helped a bit. Good luck to you both.
That is what I would like to know too...I usually get tender breasts 2 wks b4 AF then this month nothing till today and Im due tomorrow so Im telling myself its just a slight variation and did have a bit of cramping on and off but secretly hoping Im pregnant. Is a doctors test more accurate and when can first response be used?