Not having symptoms isnt rare or something to worry about, I didnt with my first 3 babies, consider yourself lucky =), congratulations!
all preagnancy are different with my 1st pregnancy i got the symptoms when i was 8 weeks with my twin girls i got the symptoms the last two months this is my third pregnancy currently 19 weeks and havent had any symptoms at all
I didn't have symptoms and I'm 18 weeks and everything is fine. So don't worry too much.