I find that walking and pacing really helps. Rearranging my sentences if I come up on a block. If you give them a disclaimer on your speech, that’s totally cool; especially if you’re cool about it yourself. You can just ask them to be a little more patient and understanding. I don’t envy your position, but know that it’s going to be over and when it is you’ll be able to breath again. Oh yeah! Breath! Seriously! Breath in between each word if you have to. Change your cadence. Bring a water with you and take a sip when you can’t say something. Break the ice with a joke. Best of luck to you. You got this, don’t be defeated.