How do you know if I have a thyroid condition?

I eat 1200-1400 calories a day. I workout for about 60-90 mintues 4 to 5 days a week. I drink about 6 to 8 glasses of a water a day. I have not lost any weight. I am currently 5ft 6 and 133lbs. I need to lose 5lbs. I have trying this same diet for months. I eat fiber, protein, fruits and vegetables. Please let me know if I should get my thyroid checked out. I think I am out of options.