help!!!

Hey everyone,

This is going to be quite a story, but otherwise my question can't be answered properly.

I've been on the pill for a year now (ethinylestradiol/levonorgestrel 0.03-0.15).
Because I had unpleasant side effects and couldn't go to work often due to the stomach pain, I switched to a lighter pill (ethinylestradiol/levonorgestrel 0.02-0.1).
I'm now at the end of my third strip (should get my period on 23-08) and will then be 3 months late.
Yes, 3 months. Since I started taking this lighter pill, I haven't had my period anymore (only had a little bit of bleeding every other day in the second week of my second strip) and nothing else since.
I took 2 tests because well, regular intercourse means there's always a chance, no matter how small.
But both were negative.
Now, these were from Action (we just moved in together and aren't exactly rolling in dough, so we thought we'd keep it as cheap as possible) and I have no idea if those are that good.
For the past week, my stomach has felt very heavy and I've been eating extremely a lot in the last few days. Also, sometimes I suddenly have to pee really badly and then again 10 minutes later (and then a liter).
I've also had stabbing pains lower in my stomach (especially on the left) so severe that I doubled over. It feels a bit like my stomach is stretching from the inside.
Anyway, I need to go to the GP anyway to get my new strips and discuss my experience with this pill.
But I wanted to know what you all think, can I be pregnant or is something else going on?

Thanks in advance!