Not necessarily. The HCG has to be high enough to be read by a HPT. Most of them will not read until you have a level of 25 HCG (some WILL read at 20). It is for this reason, that the experts recommend you do not perform a HPT until after you miss your period as the majority of chemical pregnancies will end within a couple of days of your normal period.
yes
nothing it will always be positive.
Color changes
The pregnancy symptoms may or may not start by three weeks of conceptions. But the urine test of pregnancy is almost always positive by this time. You can repeat the same after three days, if negative. By that time it should be almost invariably positive.
Pregnancy can do this.
there is always an error factor but with a blood test you can be pretty sure its correct.
Yes. It is always better to go an consult a doctor if you are in doubt.
It is common to have light bleeding and cramps in the early stages of pregnancy. The blood is usually a dark almost brown. But not always.
No. Implantation does not always cause bleeding, a late period with a positive pregnancy test is the only way to be sure "implantation" or pregnancy has occurred.
In a chemical reaction sometimes old bonds are broken and new bonds are formed.
A new compound is formed
good advice - know that everything always happens for some kind of reason , good or bad.