IF you’re cool on the idea, then don’t do it. It sounds like you’ve already indulged him enough in his sexual experiments.
You need to be confident about your relationship with this man and don’t let him lead you a merry dance.
If you try something in the bedroom – at his suggestion – and don’t like it, you must tell him so.
If you put your foot down and lay out clear boundaries, he should understand and respect them. If not, bin him off.