The signs you mention are subjective and not a sure thing, but getting fat in the middle, and enlarged, pinker teats are often observed signs of pregnancy.
More diagnostic methods would be ultrasound (usually after 25 - 30 days is more accurate) or xray after 45 days. I personally have not had much experience with the Relaxin test. I do know someone who tested her bitch with the Relaxin test, she was negative for pregnancy, so they vaccinated her. Lo and behold, she WAS pregnant, fortunately no problems from being vaccinated, but I don't know how reliable that test is. I tend to feel more comfortable with the "sure thing", ultrasound or xray, to diagnose pregnancy.
