Forgetting about cheating

Just today I cheated on my boyfriend. With my ex-boyfriend. The problem is, I don't think that I ever really got over my ex-boyfriend, and recently he admitted to loving me, although he was the one that broke my heart before. Unfortunately I am in a position whereby I have to see my ex-boyfriend daily, and therefore this incident wasn't planned. However, it has been building up to this for a long time as we've admitted we still have feelings for each other. I have been with my new boyfriend for 4 months and have never been happier, and he really brought my happiness levels back up after my break up. I am so against cheating and disgusted at myself for allowing myself to do this. We just kissed and I laid with him, but I always stopped myself from doing this before. I vow not to tell my boyfriend, as I've read that it is best to keep the guilt to yourself as letting the other person know only makes it harder, and they don't deserve that. My boyfriend doesn't deserve this, he is amazing, I just can't help having strong feelings for my ex. I feel so guilty now that I know I won't do it again. I'm just here because I need reassurance that I can live with the guilt and move on from this without telling my boyfriend.