Thyroid problems commonly cause disturbance of the menstrual cycle, and untreated or insufficiently treated thyroid problems can be responsible for miscarriage or problems in a pregnancy. It is very unusual for doctors to be unable to make a woman ovulate because the drugs we can use are really very powerful, especially those given by injection. There are, of course, exceptions and even in the most up-to-date IVF units, there are a few patients every year who do not seem to respond.
One reason for this could indeed be a thyroid problem and the current view is that an underactive thyroid should be treated quite aggressively in young women, especially those trying to conceive. You should have your blood tests repeated to find out whether you are on the right dose of thyroxine. Regular tests are usually needed over the first year until things become stable. Your TSH level should be less than 3.
It is definitely best to postpone trying to become pregnant until you know that you are on the right dose of thyroxine. This way when you do become pregnant you stand the best chance of having a successful pregnancy. Once you are on the correct dose of thyroxine, your cycle should return to normal.