I am between two and three weeks late,one pregnancy test is

Hi,I'm 20,married,not on birth control.
I'm not exactly sure when my last period was,as is I work a lot
And don't have time to do the right thing,and keep track of it on a calendar.
The last period I "remember" is November.
I might have had one in December,but I just don't remember it.
I haven't had one in January at all, no cramps,no bleeding of any kind.
I feel as if I have gained a little weight though,maybe 2-4 pounds,not sure how much,but I do notice I feel heavier.
I'm a thin girl,I don't gain weight very often. I was wondering if that could delay a period,or cause it not to come ?
Also if you know of any uncommon pregnancy symptoms,please list
some.

thanks.