I'm not an expert by all means....I can only repeat what I researched and read from various sources:
Some goats, even when successfully breed, may still show signs of heat one more time.
In a healthy goat, appetite increase.
Goat become more "momma like", more friendly.
When you top/press on their belly a front of udder, on a right side, it suppose to be hard.
(When mushy, no babies.)
In a last month, the udder start to develop; first a little plums, then a little lemons, etc....
Finlay, you will notice them being fat and can feel baby moving on a right side.
Lastly, there is an option to draw the blood and send to some Biological Institute
for the cost of $14.00 you will get definite answer.
I don't have the address on hand right now. As to me, I would faint first, before I can gain a courage to draw blood.
I'm just waiting till my goats become very, very fat and develop udders.