22 days late 4 negative tests?? Ideas?

I am now 22 days late (just over 3 weeks) just wondering if this could be anything else other than oregnancy Iv took 4 tests and they have came out negative the cheap ones and the clear blue ones, Iv been to the doctors 3 times and they keep telling me too wait another week. My period are usually normal and if I am late it usually 2 days max! Somebody help!!? Iv had a few symptoms like being really tired, hungry all the time feeling extremely bloated and most of all moody as hell.