A thyroid cyst is a fluid filled sack. A complex cyst is when both fluid and solid cells are present. Fluid filled cysts are rarely cancerous.
I'm sure your doctor will refer you to an endocrinologist, or surgeon. There will probably be a fine needle biopsy. Thyroid cancer, if that's determined, is the easiest of all cancers to treat, because the thyroid is simply removed and you're then put on replacement hormones.
I know it's easier said than done, but try to relax.
Postpartum thyroid trouble is common, I had it after my 2nd child. You could have the nodules tested by FNA biopsy, but for now there is really no huge red flags. They will probably watch them and see if they change. If they get bigger, turn vascular, or get irregular borders, then they will probably want to biopsy them.
My 27 year old daughter had tiny multiple nodules two years ago that were discovered during exams for her gallbladder which was removed during that time. The nodules were too small to biopsy but she was told to come back in a year for another ultrasound. She became pregnant and had a baby so that took up another year of here time where she did not get her thyroid rechecked until recently. Now, the nodules are over 5 centimeters. Very complex with very irregular borders. She is tired all the time and has difficulty swallowing. No hoarseness in her voice but she has been aware of her thyroid being too large for more then 8 years. (Sigh) I never knew this.
Now, her GP wont let her wait to go see an endo. He told her to get there now.
I had my thyroid cyst 5cm biopsyed & it came back negative for cancer.It was done by ultra sound guided needle.Mine was part fluid & part solid.Then I find out this test is 80% accurate not 100% like I 1st thought so still a little worried.All my blood work for thyroid function came back good so I think I am okay.I will be seeing an endocrinoligist soon.I wish you all the best & I know what you are going threw because the waiting is got to be the hardest part.Even if it is cancer,thyroid cancer is the one of the most slowest growing & easiest to fix.I will say a prayer for you,all the best.