Bleeding 1 week after period...been on POP for 2 years, never happened before-am i pregnant?

Hi,

I'm really concerned!can anyone help?

I'm on the POP contraceptive, (micronor) have been for 2 years, im 22 in a long term relationship with boyfriend, and my periods are generally like clockwork- 6 days on, start on 20th of each month give or take a day.

I had my period this april and it was noticeably short, it lasted about 3-4 days, so i noticed it was strange. in hindsight this past few weeks, maybe during my small period iv only every been late taking my pill maybe twice, by about an hour. (only have 3 hour window for effectiveness), so there is a small chance. However, i think its the psychological thing that im on period therefore not having sex. Stupid I know, but it only renders it ineffective for 2 days after you're late.

Anyway, we had sex about 2 days after my weird period (last thursday night) I'd done my pill on time that day and since then fine.

However, 3 days later (monday- todays weds) I've experienced increasingly painful dark bleeding to the point where i needed to use a tampon last night in bed. It's brown, when i wipe its red. And its sore.

its never ever happened before and i am freaking out.  I did go walk-in yday and the nurse put it down to nerves for an exam i had the monday and suggested my stomach upset on the day i started bleeding meant i'd not ingested the pill...how? When i take it at 11pm and the upset didnt happen till 9am the next day, coinciding with the bleeding?

In panic i did a test last night and its negative-but does my messed up period etc mean that's innacurate and it's too soon?

I know this is confusing as hell but please give me some advice i am beside myself and my boyfriend isnt really very sympathetic!