Hetergeneous diffuse echotexture means your thyroid gland does not contain all the same type of tissue. This could indicate inflammation of the thyroid. This is, often, seen with the auto-immune conditions, Hashimoto's or Graves Disease.
While the report doesn't, specifically, say there are nodules, it does say there are no "suspicious" nodules, which leads us to believe there are some nodules, there's just nothing to be concerned about. Thyroid nodules are very common with, both, Hashimoto's and Graves Disease.
It, also, states that your thyroid gland is at the upper limit of normal size, which indicates there may be some slight swelling of the gland... Swelling and/or inflammation are common with Hashimoto's and Graves Disease.
Can you tell us why you had the ultrasound? Have you had thyroid blood work done? If so, you should have had, at least, Free T4, Free T3 and TSH to test for thyroid function. If your doctor is really on her/his toes, s/he may have ordered antibody testing to determine whether or not you have Hashimoto's or Graves Disease.
Last, but not least, do you have symptoms of a thyroid condition? If so, what symptoms do you have?
Are you currently taking a thyroid medication of some type - replacement thyroid hormones, anti-thyroid medication, etc? If so, what medication(s) and dosage and for how long have you been taking the medication(s)/dosage(s)?