Periods have disapeared, feel sick, not pg.

[Marne]

My period is 3 weeks late, i feel sick, bloated and have been having stomach cramps for 2 weeks as well as lower back pain. I have taken 2 pg tests (both neg) even though there's not much chance of being pg. I feel like sh*t, i feel worse in the mornings, the back pain is worse in the mornings and i seem to pick up as the day goes on.

Any idea what this could be?

Im 27 years old and very healthy.

Bump, i just googled and came up with POF ( i really shouldn't google)

Turn out i have got a nasty Kidney infection and possible kidney stones, GP has given me strong Anti-biotics and i have to wait for tests to come back.