worried

ive ad a tubal ligation done 2 years ago wid the clips and over the past 3 weeks ive been getting really tired, sore breasts, moody, bad back, heartburn and fluttering in abdomen, constipation etc.... i ad a few days 2 weeks ago where i was on a period but it was lighter and shorter than normal, i also av vaginal discharge more... ad blood test done and urine tests 3 weeks ago but they were negative and i took another urine test last week n that was negative but still feeling these symptons but from this morning ive ad a really bad stitch like cramp in my lower left side... im really not wanting anymore children as ive ad 6 already n im only 30 years old , im due to go for an ultrasound scan this week but ive been checked for infections and they are clear ... i relly do feel pregnant im always really exausted and cry over spilled milk please help anyone whos in same situation