What to do if i heard that mouth ulcers aren't contagious but can you get genital herpes from mouth ulcers if you engage in oral sex when ulcers are present?

Different ulcers: A ulcer means that the skin is broken. you can get an ulcer from trauma, a canker sore or from herpes just to name a few. If you don't know what the ulcer is from, better to be careful. Not all are contagious (like trauma is not) but herpes is highly contagious.

Yes, its possible.: You can get genital herpes from oral sex if the mouth ulcers are herpetic. It is not always easy to tell if mouth lesions are herpetic. Many recurring mouth ulcers come from a herpes virus. Oral sex when mouth lesions are present should be avoided.