My biggest secret

I dated a guy and in sake of keeping this anonymous I will call him Jack. I am currently in a serious relationship with someone I shall call Will. Jack and Will are best friends. I dated Jack for a long time and he was the very first person I ever loved. I broke up with him because I was in a dark place and I relied on him too much. I didn’t love again after him until Will. My relationship with Will is now my longest and I love him more than anything. It wasn’t until a week or two ago that Jack added me on a social media account. Ever since then I can’t get him out of my head and I feel unfaithful. I don’t want to think about Jack and I know your first love stays with you but I don’t want him to. Anyone have any advice?