I Have Missed Two Periods, Have Got Severe Leg Cramps,

I have missed two periods, have got severe leg cramps, fatigue, bloating, headache,backache. I did the pregnancy test 3 times, it came negative. These symptoms started one week back. Before that everything was normal. I had my first baby last october and i had gestational diabetes. Today when i check my blood sugar it came little high. I Have got achy legs.. My mother also didnt get positive pregnancy test result at her 4th bay..it came in ultrasound in her 4th month..so may be i might be pregnant. I live in london.here NHS doesnt look into the matter seriously they say urine test is negative so u r not pregnant..i dont know what to do