Your blood pressure is alarmingly low.. You should first of all consult with your physician under whose guidance you are taking thyroid treatment and monitor your B.P. on daily basis for some time. It can be associated with low thyroid functioning . you can also go for a haemogram to assess your blood picture thoroughly... You may be anaemic as well too. Improve your diet in quality ... Like hv at least 2 glass of milk or curd daily. If you are a non vegetarian eat an egg daily... And please do not go for dieting or be calories conscious till the time you recover from your headaches and other problems.