How would you approach this !?

Ive been in a relationship 10 years with my man. Sex gets a little vanilla and ive been dying to spice it up male or female , how would i bring this up to my partner ? I love him hes my soul mate im not the jealous type actually ive thought about him fucking someone else and got turned on by it and vice versa im kinda scared to bring this up and see what happens in the passed ive sexted another guy and he was pissed but we alsoo watch live porn together