Jealousy is a hard thing to pin down. It can rear its ugly head in a moment and be completely unpredictable. It can be the downfall of a relationship. Eating away at the trust of a relationship until there is none left.
A little jealousy within a relationship is normal. Out of control, calling 22 times a day is not. No one should have to put up with it. Don't believe that if you change you behaviour that the jealousy will go away. It won't. The problem is not the way you behave, but their out of control reactions.
The only way you can help the person is to try and understand where the jealousy comes from. What is making them feel this out of control way? Is it because the person is feeling guilty themselves? Are they projecting their own guilt onto you? Are they stepping out on you? It could be that their guilty conscience is making them project their feelings onto you.
Have they been burnt before? Someone who has been cheated on before is more likely to believe it will happen to them again than someone who hasn't. They could have been hurt so badly that they have lost their ability to trust anyone. Even the person they proclaim to have feelings for. As a result anyone who they have a relationship with they totally cling on to.
Insecurity in a person may cause them to act in a jealous way. If someone feels they are not desirable then they doubt that other people find them desirable. In the back of their minds they believe that they have to hold on tight to keep them. Too tight sometimes. They have to keep control of every little thing or they will be left.
It is always the mother's fault. Just kidding, but how their parents brought them up also could have something to do with a person's jealousy level. If something terrible happened in childhood it really leaves a mark on a person. A mark that could affect how they deal with people for the rest of their lives. If we feel abandoned by our parents or are negatively affected by our parents divorce or had parents who were not emotionally available to us during childhood it could lead to being overly jealous adults.
Now that you know some of the reasons why a person is overly jealous the next step is knowing how to deal with it. Jealousy usually crops up when there is no real reason for it. No way to predict. No matter how many times you tell them there is no real reason to be jealous will not change how they think. No matter how many times you apologize will it change their belief that there is a valid reason to be jealous.
So what can you do? Stop enabling the person. Tell them that there is no reason to be jealous very calmly and that you will not be controlled by their jealousy. Secondly, set some ground rules. Tell them how much time you are going to spend together and how many phone calls a day are acceptable. Being open and up front will be helpful.
A little jealousy is normal in any relationship, but it has to be kept to a reasonable level. If it ever grows to an unacceptable level then it might be time to move on.