Thyroid problems are a possibility. What medication have they put you on? Some medications take time to build in your system before you see results. It took me a year from the time I was diagnosed until the treatment had a truly noticeable and positive effect.
AT THE MOMENT I AM NOT TAKING ANY BECAUSE I THOUGHT THAT I WAS PREGNANT BUT 2 NEGATIVE TEST PROOFED ME WRONG! I AM A BIT STRESSED OUT THOUGH! I STILL HAVEN'T HAD MY PERIOD.I AM ONLY SEEING THE DR ON MONDAY AGAIN.BUT MY HAND REALLY HURT THE RIGHT HAND IS SWOLLEN AND THE RIGHT FEET IS ALSO SWOLLEN,I HATE THIS! IF IT IS INFLAMMATORY ARTHRITIS SHOULDN'T THEY HAVE FIXED IT BY NOW???DO U THINK I COULD BE HAVING TYRIOD PROBLEMS - CAUSE I SAW ON THE NET THAT THIS COULD ALSO CAUSE YOU JOINT TO SWELL AND MISSING YOUR PERIOD?
This could be arthritis. What medicine have they prescribed for you now? If this has you very stressed out (which I am assuming from your post) that could cause you to miss your period. If you have been active, you should take a pregnancy test so you can rule out that possibility.