It seems you are having similar to what I have, back pain, excess gas and cramps. However I am abotu 80% sure I am pregnant, I just am playing the waiting game to find out.
I would take a test, if it comes back negative wait 5 or so days and do another.
However it is a little early for every thing.. But I am not one to commet as I have been havgin signs of it from only 8 days after I ovulated.
Best to wait for your period, if you are late take a test, but dont stress too much about it, stressing will only make you late and inturn get your hopes up needlessly.
But good luck!