Insecurity towards partner

Is this a phase ? Since being pregnant I've felt 10x more insecure that he will leave me for someone else. I really hate feeling like this :( ever since I started getting bigger it's making me feel worse about it because he doesn't seem interested in the bedroom department anymore. When he goes to the gym I do worry about it. I hate feeling like this I don't know if it's the way I perceive myself or not.