I've been done oral sex with 5 guys and have a canker sores in my mouth is it because of lack of sleep or the sex?

Maybe Both: What patients refer to as canker sores are generally apthous ulcers that are stress related (like too little sleep). However, some patient think it is a canker sore but it is something else. It could be an std. You need to see your dentist or physician and let them check it out.

Both possible: Or it could be unrelated. The cause of canker sores is unknown but stress, like lack of sleep, tends to trigger them... If they continue i would suggest seeing a physician for an evaluation and treatment if needed.