Having to Give Constant Reassurance
An insecure person may exhibit feelings of worthlessness. He may believe you don't really care for him. After all, he doesn't believe in himself. This can cause problems, because he doesn't really trust your intentions. You will have to reassure him all the time and let him know that you do care. His trust issues may drain you as you find ways to show your love for him.
Jealousy and Control
An insecure person may display feelings of jealousy. Because he questions your love, he may feel jealous when you do something without him or go somewhere with friends. He may feel as if you will leave him at any time. His jealousy may turn into control as he tries to keep you with him all the time. For instance, he may question you extensively about your whereabouts on a particular day.
According to an article published on MedicineNet.com, a person with insecurity issues may be at risk for cardiovascular problems and other diseases. You may have to worry about his health in addition to other issues. His worries about rejection and his constant neediness place him at risk for high blood pressure. He may even develop ulcers.
Relationship Does Not Progress
An insecure person does not believe he can be loved. Thus, he may put up a wall around you, keeping you from getting too close. He may fear you hurting him by leaving him. He may seem cold by not allowing the relationship to progress. You may want to get closer with him and move to the next level, but his insecurities may stop the relationship from moving forward.