BP concern (hypertension) Side-effects?

By BP while sitting is 148/100 and while lying down is 135/90 .. I always found its above 140/95 + .. I ignore it earlier, I don't have issue , but I am concern about it might in future it would be cause of something... I am also a thyroid (thyronorm), fatty lever  patient and taking medicine for the same thyroid only .. (thyronorm 75 Mcg) My help me in this ..how can I control it permanently , Is it possible without medicine .. Pls advice .. If medicine is required what medicine should I take which have less side-effects ?? What would be cause of hypertension in my body , I am just 38 .. One more question, why BP is difference when We sit or lying down during monitoring.. I m not taking any medicine for BP. Few Month (6)back I felt some kind of pressure from my heart side but in ECG and other heart test nothing comes ..