Why not sex fluid come before doing sex

I am married. My problem is when I would like to sex with my wife no sex fluid come infront of my penish. Some times I found a single drop of fluid. Why this occur and why do not come fluid can you five me any advise or prescrib any medicine for it.

When a man gets excited or sexually aroused, his penis gets hard, this is called an erection. When a man has an erection, sometimes just a bit of fluid comes out, this is called precum. Thi would be the single drop that you found.
To get more fluid, the man must ejaculate. To ejaculate you must have an orgasm. You can either masturbate (stroke your penis) or have sexual intercourse (penetrate your partner). The stroking of the penis will give you an orgasm and this will release a white fluid called cum.