Feeling insecure about husband

I’m in a very good relationship with my husband and we have been together almost 8 years and married for nearly 2. He has done absolutely nothing to warrant me feeling this way but I keep thinking “what if he finds someone better than me” and he’s currently away for work and I keep picturing him cheating on me and having a one night stand. I just feel so insecure and not good enough for him right now and I have no idea why I feel this way! he is an amazing husband!!