Im straight but wonder what it'd be like to kiss another girl! Ive bin in a relationship 4 6 yrs wht do i do?

ive thought about bringing another lesbian into the "bedroom" because thats all my boyfriend could think about...how cool it'd be when i told him i thought about it! but im scared it will destroy my relationship! What should i do? N im not even sure thats for me! Ive always wondered what it'd be like to kiss another girl first n formost! Im so confused!