Have Palpitations, Chest Pains. Diagnosed As Borderline Hypothyroidism. On Levo. What Does It Sound Like?

Hi, last summer I was diagnosed as borderline hypothyroid and put on 25mcg of levo, they gradually increased my dosage to 75mcg. However, although for the first 6 months I felt great, I ve suddenly not been able to sleep, I have heart palpitations and yesterday chest pains - I felt even worse than before. Subsequently, I ve decided to stop my thyroxine for a little while as my last blood results showed that I was probably on too high a dose anyway and the doc suggested I decrease the amount straight away. I had already decreased to 50mcg but still two weeks later I still feel dreadful which is why I ve decided to give it a break for a while. I will probably go back to 25mcg after a few weeks. Question is do you think it s ok to stop for a while considering I was only marginally hypo in the first place? Do you think supplements such as L-Tyrosine are a safer option for me? Would appreciate any advice you can give. Many thanks, Judy