What Causes Erectile Dysfunction?

hello

sir i m 38 years old married

i stayed in russian since last 10 years, i got married 5 years back

now i came last week back to india for forever.

now i m facing problem in sex? i can able to make sex with my partner because my penis is not so big and its not becoming thick everytime its loose i cant feel anything even when i sleep with my wife or do sex from up than also no reaction from my penis, so pls suggest me what to do