If you have hypertension you need to manage it with medication like acei or arbs. If htn is left unmanaged youll end up with lvh and other problems.
For the tachycardia, how fast is your heart going? Tachycardia if its frequent enough (constantly day and night) can cause heart failure too. It sounds like you could have anxiety, possibly panic disorder if you have random panic attacks with a lot of physical symptoms. Beta blockers like propranolol, metoprolol, atenolol, or nebivilol are excellent for controlling a fast heart rate by blocking the effects of adrenaline on the heart. Nebivolol and a few other beta blockers have intrinsic sympathomimetic effects which means they wont lower it as much as a pure antagonist like propranolol.
I would get checked out by a doc soon just to make sure it isnt something serious. Check your hr and document when it happens and any additional symptoms. Dizziness, lightheadedness, feeling like youre going to pass out, or any chest pains are important to mention. Check your bp and if its high take a few deep breaths and check again and write it down.