Should I buy another pregnancy test?

My period should have come last monday, it is always regular and comes on the day. I have a 31 day cycle and bleed for 5 days. I am not on the pill but my boyfriend and I use condoms (and we haven't noticed that any of them have split). The week before my period I always get sore breasts, so I first noticed something strange when they didn't start hurting. I usually only cramp on the first day of my period, but last monday i started cramping with no blood and my breasts started hurting. I felt generally under-the-weather all week, with cramping, sore breasts, fatigue, slight nausea. On thursday evening I gave up and bought a home pregnancy test, but before I got to use it (I was in work), my period came.  Not wanting to waste the pregnancy test I used it anyway just to make sure, the result - negative. I have very light periods anyway, so it was no lighter than usual, just really bright red (rather than the dark red it usually is). However today my period has stopped, it only lasted 2 1/2 days ... should I buy another pregnancy test? Or wait and see if it was just a one-off thing? I am not cramping anymore ... and other than feeling ridiculously cold (I am sat in two thick hoodies) I feel absolutely fine, but have been making frequent trips to the loo.

Note: I am away from home and am not registered with a GP here, and so can't go to my GP for advice.