Hi, thanks for writing in with your concerns. If your fiancée and you have not had any sexual contact with anyone before, then there is no risk of sexually transmitted infections (STI) being passed between you. Ejaculating within 30 seconds of your first oral sex is not unusual. Learning about your own and your partners body is one of the very exciting  aspects of sex.
Using a saltwater mouthwash and turmeric would not prevent or cure an STI. For effective treatment, STI’s are treated with antibiotics known to cure the specific STI.  Hope this helps and please write back if you have any further questions. Health Nurse