Hi Tillie,
For the cost of a stick test I would do another (but make sure it's the ultra accurate, first-day-of-missed-periods type and do it t'morrow morning). I got negative stick tests for the first month I was pregnant with my son. Otherwise see a doctor to get a blood test to know for sure. It'll at the very least put your mind at ease. I think any ferns suggests oestrogen...it's only pebbles otherwise. Sore, full boobies are a sure sign of pg or a period too I suppose (my first sign was always that). Better to be in the know than stressing or dissapointed. Good luck!
Zena