For some time now I have lost interest in sex and this is affecting my relationship.?

Answer 1

Bummer. Maybe try new things, more exotic or extreme things in the bedroom. Maybe you will find a new fetish and you'll be right back on track.
W.

Answer 2

You should see a doctor about it. There could be a medical reason. If you are just stressed or over worked, try getting away with your wife for a few days. That generally releases the tension and makes you more open to relations.

Answer 3

.... dude go to the doctor... almost all loss of interest in sex is medical... it may be hard to believe but it is go talk to your doc.