dear patient. i understand your problem. according to my experience the major cause of your bladder infection 1.spastic bladder where your bladder is inefficient in emptying the bladder completely,leading to retention of urine in the bladder and growth of infection. 2.another cause possible is that you might have some small bladder stones or kidney stones which are predisposing to recurrent infections.to rule out i request you to get usg abdomen. 3.with age immunity of the body decreases.this is a very important cause. i suggest you to take high protein foods,fresh fruits and vegetables,avoid red meats,take chicken and fish to improve your immunity.take one tablet of multivitamin everyday. 4.low blood pressure is also the important factor. since you may be on heart medications sometimes they can reduce blood pressure levels below normal as the side effect leading to decreased function of kidney and decreased urine production leading to infections. try to keep your blood pressure in normal range and check it regularly. 5.take cranberry juice regularly .it is known to prevent recurrent urinary infections.