imagination and self - pleasuring, I tried to pleasure myself and I was not able to ejaculate

I am 32 years male, in my collage days I had habit of sex imagination , I was totally addicted to that hence I always faced problems of nightfalls , recently I got engaged ,before marriage I wanted to take doctors advise hence I went to doctor he told me to do masterbation for every alternate day .I tried but even after 45 minute I was not able ejaculate then again on alternate day I tried but result was the same is it normal secondly can excessive imagination lessens your sexual desire , and lastly will it affect my sexual health after marriage