It's HIS job to check who he interacts with, not yours. If she brings it to the front door of your personal space, then and only then should you be checking HER about anything. Your man cannot control a woman's level of disrespect, so don't fault him for women who pursue ruthlessly, but he CAN control entertaining her after the fact of peeping her angle.
The last thing you need to concern yourself with is explaining to various women your worth. For one, they are probably already aware of you and could not care any less, or they do not know about you because your man has omitted this information. Either way, both situations do not require your action. If a man is allowing a woman to share your goods, then this is cause for approaching your man. You make yourself appear desperate and needy if you accept a man's behaviors that exhibit cheating, but reward him with jealous rage and empty threats of leaving the relationship.
Know what you deserve and recognize when you are being played. A woman's intuition is nearly always correct, and this is a gift men can never obtain. If you feel something, then inquire. If he denies it, leave it alone. If you feel the urge to snoop through his things, you are displaying that you do not trust him. When this happens, you become insecure and suspicious. If you stay after he actually cheats, yet fail to forgive him because you revisit the hurt often, then the problem moves from you leaving a cheater, to you being the issue because of trust issues. The focus will then be completely removed from the cheating or suspicious behaviors and be transferred to your insecurities as the blame for the relationship not working out. Be as honest as possible with yourself. Can you handle a man with a lot of female attention? If the answer is yes, then be sure you have a man who knows that his role is to reassure you with his actions that you have nothing to worry about.