it is very very possible to not have any symptoms at all, I had my first baby when i was 17, I had some symptoms with her, but mostly kept them hidden from my parents, then I got married and we decided it would be cool to get pregnant on our honeymoon, well when we got back I took a test just for the fun of it and it was positive, way early right, nope went to the doctor and I was 5 months pregnant, I had my period all 5 months, no sickness no nothing, she is very healthy thank god, and so is my third child who I had absolutely no symptoms with either except I had missed my period
my results - 3 kids, 1st two = 14 months apart, 2nd - two 11 months apart..