Welcome to our forum Justjade 90
I am sorry you have just been told you have hypothyroidism (underactive thyroid gland). The doctor was negligent in not notifying and treating you when first diagnosed.
The thyroid gland is very important as it controls all our metabolism and it also causes female problems, i.e. periods, miscarriages,premature births etc.
When you are treated properly and on an optimum of medication which makes you well you should be able to carry to the full term
It is really shocking and negligent that you went unmedicated for four years.
You have to read and learn as much as you can which you are doing today. The members are very helpful and will assist you in whatever way they can.
I hope they checked your baby's thyroid hormones too. I believe they usually do it at birth nowadays.
When you are due for your next blood test, you should leave 24 hours between your levothyroxine and test. Have the test as early as possible and take levo afterwards. Ask for a copy from the surgery of the results, with the ranges, for your own records and so you can post on the forum for comments. If you haven't had a test for Vitamin B12, Vit D,iron, ferritin and folate ask for these too as we are usually deficient.
Take levo first thing with 1 glass of water and wait about an hour before eating. Or you can take it at bedtime, last having eaten 2 hours before. If you take supplements or other medications leave 4 hours between taking levo.
I think you have this condition but maybe when you are on an optimum dose of levothyroxine it might not be so bad. I think because you've been untreated for 4 years things have gone a bit haywire.
If you copy and past the first part of your post into your Profile, it will enable others, if they wish at some point, to look at your history and it saves you having to repeat answers to questions.
Yes it can cause premature births:
Hypothryoidism can interfere with fertility and increase the risk for miscarriage and preterm birth.