General Weakness

I am 36 years old.for the last one or two years i feel physical weakness.I feel tired when exposed to physical work.I also feel that my sexual desire is decreasing day by day.During the day my disposition changes, at one time i feel angry at another time i feel worried and then i feel ok.i have no major disease except that my eye sight is weak and hace partially lost my hair.I am married having two kids.Most of the times i remain in disagreemnet with my wife on domestic issues.I take full sleep.Like to watch TV and Cricket.I also like to spend time among friends.I like both salty and sweet food but prefer to eat salty food.I use to remain mentally fresh butfor the last couple of years i have become dull.I also feel sexually week as feel no desire for sex for long periods say a week or so.Please advise.