Heart failure itself decreases your cardiac output and known to cause such symptoms. Symptoms are more pronounced when u have associated hypotension. So I don t know ur previously hypertensive or not. But the drugs coreg, lisinopril, aldactone all acts as anti hypertensives along with acting ad anti failure measures. So abrupt drop in blood pressures us expected. So please stop these medications, consult your cardiologist and get a 2d echo to reassess cardiac function.