Can I cheat on my husband online?
That would not be good. Can you not have sex with your husband instead of cheating on him?
No, I'm almost never interested in sex with him
Not wanting sex with your husband is sometimes inevitable, especially when there are so many other men out there who are more desireable.  Cheating is pretty lame to go about it, I would like to inform you that it will only cause a deeper issue later on and destroy your entire marriage. Get a divorce first and foremost to make it legit first.
It's fine. Someone's going to be lying in the marriage anyway might as well be me.
Nobody has to lie in the relationship though. But that you think that shows that you have a lot of problems in your relationship that cheating won't fix. You need to decide whether you should continue your marriage not whether you should cheat.