Hello.....I Have Always Been Pre Hypertensive - But Before Xmas

Hello.....I have always been pre hypertensive - but before xmas did a course of weight training - which I felt got too much for me - then it was xmas and I was drinking and eating bad foods - I started to feel light headed and went to get my blood pressure checked. It was 166/85.
since then I have been home checking it and though the systolic number is going down - the bottom number is remaining at 90-95. the doc has told me to take Losartan 25mg but I am worried about side effects. I have been eating fruits, veg, fish and no salt or caffeine or alcohol since xmas. I am hoping to get my bp back by lifestyle......but I am worried about that bottom number. any thoughts