I feel like they are interested in that person and accuse them of it. I do not want to go to counseling and would rather do it on my own with a book or other self-help method. You have correctly identified part of the source of jealousy, Namely, feeling threatened. Often underlying the threat is a profound sense of insecurity. Insecurity about one's masculinity, one's attractiveness, about being abandoned, about not being good enough, and so on.
Many men present themselves to the world as full of self-confidence.
That self-confidence, however is often a veneer. The underlying insecurity raises the level of vigilance to real or imagined threat. You are always on the alert and feel the need to protect yourself. Your method of protection is to be angry with the person who is stimulating your insecurity. Rather than focus on your feelings of insecurity, you blame the other person and go into attack mode against the threat.