Disappearances for a few hours a couple of hours a week? Coupled with a butterfly feeling in your tummy?
Does it equate to infidelity or is it just a sign that it is coming?
Infidelity is a problem of partnership. Whether it be a mismatch of two people or one or both of you are just incapable of having a real relationship.
So what is a real relationship? Everyone may want different things but we can agree that the two people must want the same outcomes.
“Outcomes” mean running in the same direction. You don’t have to have the same hobbies and talents but you have to agree about the big stuff, like how to provide for your family.

The problem is that we often choose someone based on sexual attraction and while that is great fun, it can lead to disaster later on, especially if you move too quickly and end up with some distorted commitment to each other that you cannot get out of, like a child, or a mortgage or even worse, an abusive relationship.

If you are stressing about a cheater then you have no future with this person. Period. Full stop. Move on and get over this wanker.

If you have suspicions, chances are you are correct. The only time you might be wrong is if you are the perpetrator and you will always be suspicious because of your guilty conscious.