High thyroid

So I have had high thyroid so far throughout my pregnancy and my doctor doesn’t want to put me on any medication until closer to the end of the month to the beginning of next month when they test my blood again which I am 15 weeks today. Well this morning I went to work and my heart rate was feeling a lot higher than normal and I had shortness of breath and I got to the point where I got dizzy and thought I was going to pass out, so I called my doctor and they just told me to go to bed rest and if it doesn’t help then go to the ER, but I’m thinking it’s my thyroid acting up ... so my question is how long can I go without harming my baby bc my doctor isn’t going to bring me in any earlier to test me so I’ve been stressed out thinking I might lose the baby if I don’t have the treatment right now