Okay so please help

My last period was on (or around) 19th Feb. I'm not on any birth control cause my Dr took me off the pill in October (from memory) and my partner and I dont really care if I fall pregnant (cause like, a kid would be cool so we dont mind what happens either way, so no we dont use anything and we're both clean b4 anyone gets in to tell me this stuff)

I've done 4 pregnancy tests and they've all come back as negative. Now, I have also been extremely stressed so I'm just putting it down to stress, but I know theres alwayd the chance that I am.

Anyone have any tips, apart from bloods being taken, that might help?