I personally felt anxious in relationships when I subcinciously knew that something is wrong. So my guts were telling me something. When I've met husband and never felt anxious because my guts were not sending me any messages. My guts knew it was right. It is important to trust your guts. Maybe rather than trying to stop being anxious examine what's going on etc are you seeing a therapist? Also how long have you been seeing this person? Is this a new relationship?