It sounds like you're almost asking two questions. i'll try to answer both and make sense, but no promises!

Anything that you say has to be agreed upon in your dynamic. If you're not allowed to say 'no' at all, ask Him what you can say instead. If you pick a phrase that doesn't break your submissive 'character' in the moment but still communicates to Him your current feelings, it can be almost anything. Examples are 'only if it pleases You, Sir' or 'as You wish'. BUT using these when He doesn't know that they actually mean 'i do not want to do this' is pointless and potentially harmful.

Which is where we start to get into safewords territory. If you're trying to say 'no' to an activity for a valid reason, or if you haven't agreed to have your limits pushed, a safeword is what you should be telling Him, not 'no'. This is more for if there's a reason that you can't do as you're told (i.e. it's unsafe, you have a phobia, something's gone wrong, etc etc etc).

The way He's acting almost sounds like a dramatic humour type thing. He might be teasing You, though i have no idea about Him and you do, it might be a possibility that you just aren't in on His joke yet. Or He might have a desire to consensually forcefully take you 'against your will' and is baiting you. Both of these options are a good idea to talk about before you assume wrongly and end up in trouble.

i think the big issue here is more why He doesn't want you to say 'no'. It could be because you're saying it in a disrespectful manner, or saying 'no' to things that He thinks you shouldn't. You do have the right to say no to anything that you're uncomfortable with or that you feel is unsafe, but these things should be talked about as far in advance as is possible. If you need to say 'no' and 'stop' during play in order to submit, it's important that He knows that really, 'no' means 'more please!'.

i think i've just made up my own questions, now. i hope i at least answered half of what you asked.