Just had period but feel pregnant. Confused?

OK so we have been TTC since we miscarried over a year ago. For some reason I just felt like December was going to be our month (loony, I know, but hey ho). Anyway, my period was due on Saturday just gone but I started light pink spotting on the Friday. More spotting (very minimal) Saturday and same again Sunday. Sunday night my period started and seemed heavy. Got up Monday, felt crappy, took day off work and the bleeding slowed right down. Minimal bleed Tuesday and stopped by Wednesday. This is really unusual for me as I tend to bleed heavily for several days before it gradually slows down to a stop. For a few days before period and increasingly now I have been feeling dizzy on and off, a bit nauseous and my boobs are larger than normal, not sore just a bit bigger and sort of tingly (only a bit) - husband has been gleefully pointing this out to me . I have been really tired after work and falling asleep on the sofa every afternoon, much to the consternation of my lively four year old and I still have mild period like cramps. Had a tiny bit of spotting today which I wouldn't have noticed had I not been looking. So I'm a bit lost. I did a cheapy i/net test last night and it came back with BFN but it wasn't first thing urine and it was late in the day. Also, I did a 'due date calculator' thing it calculated 4 weeks. Do you think there might be a chance I'm pregnant or am I just creating symptoms? Anyone ever had this before? Your stories/advice greatly appreciated. Thanks xx