11 DPO negative prgncy test. Sore/swollen breasts, cramping/twinges 2 days ago, lower backache, gas/bloating? All very unusual for me

Unprotected? Have you missed and cycles? Missed periods, early morning nausea/vomiting, breast pain/fullness, weight gain are signs of pregnancy. If you have had unprotected intercourse, I suggest a repeat pregnancy test. I f you are protected, get a physical exam.
Wait... If you suspect you could be pregnant wait one more week and repeat pregnancy test. If negative and symptoms persist follow up with your doctor for formal evaluation.

Related Questions

Is it possible to have strong prgncy symptoms — sore breasts, cramps/twinges, lower backache, bloating/gas, vivid dreams - before a positive test?

Not likely. Normally classic pregnancy symptoms don't begin until you have missed a period. Many don't begin until well after that time (when a + pregnancy test is likely). Read more...
You've proven it is. The real question is whether they necessarily mean you are pregnant. And that it can't. Those signs can all mean a variety of things or nothing at all. A missed period followed a few days later by a positive test is the key. Be patient. Best wishes! Read more...