Trying ... Desperately

So ... I've had sex a good few times in the last 2 weeks, my cycle is about 6-8 days late now. I have stomach cramps, constant headaches, constant tiredness and I have on and off nausea. I've done a home pregnancy test and it came back negative. So not sure where to go from here! My partners thinks my boobs look bigger and I am constantly bloated. I would be 100% over the moon if it were Pregnancy. But I'm not convinced I will fall very easily. Any advice would be great.