Jealousy is actually a normal emotional reaction to the biological qualifications of a human relationship. We tend to pick the least costly error over the more costly error. Confronting your significant other, especially if it's a long term relationship, about your suspicions is in fact a better choice than leaving the suspicions alone. You could be supporting a child or family that is not your own and never know about it. Acting on jealousy allows some sort of protection against that. While your suspicions will probably turn out to be false, at least you know.

Of course you could be irrationally jealous and that's bad.