Find out why u r very insecure about ur relationship? !! Was there  any issue between  u both after which u feel this this.!!!

Looks to be anxiety spectrum disorder.Anxiety can be treated with the help of psychotherapy and medications depending on the severity of the issue.

Hello, it seems like there may be some underlying core beliefs that might be causing this anxiety. It will be important to get to the root cause of the anxiety. For that, it is necessary that you see a counselling psychologist who will be able to assess for any cognitive distortions and teach you techniques so your anxiety can be reduced. Until then, doing some relaxing breathing exercises may help you curb the anxiety when it is particularly heightened.

This can be sign of obsessive compulsive disorder, you are getting obsessed about your partner, you need medication and counselling, consult a psychiatrist