Lumbosciatica and swimming: are there any contraindications?

Good day, I am 62 years and 8 months, I am retired since 01/01/2016, I suffer from sciatica lumbago, in practice I am missing the last 5 pads of the lumbar vertebrae. In the mornings from Monday to Friday I go to the pool and do about an hour and ten minutes of backstroke swimming. 1500 meters. I am 186 cm tall and I weigh 106 kg. I have been a heart patient with cumadin-controlled atrial fibrillation for about 10 years. On Monday evening and Saturday morning I do one hour of hata yoga. As a family, they tell me there are too many swimming days. What do you recommend? Baietta Maurizio, Thank you