Maybe you already know that 240 mgs is a very large dose of Armour. I couldn't say whether it's too much, though, without having some idea of where your free T levels are.
One thing I will say though, is that I think it's fine to reduce your dose a bit to see if the troublesome symptom will go away. You can always work your way back up to the higher dose if you have to.
I'm not sure I'd reduce it by a full half, though. I don't know what you mean by " i call my doctor he gave me 31/2 grain" --- 3 1/2 grains is 210 mgs, yet you say you were taking 240 mgs. Do you mean that he told you to reduce the 240 to 210 after you reported feeling hot all the time? If so - if he told you to reduce by 30 - I think that might be a reasonable thing to do.
In my own case, I was recently raised from 90 to 120, but I think it might be too much for me. I took it for 1 week, during which I had a troublesome side effect. I reduced the dose on my own to 105, and the side effect seems to have gone away. Just the tiniest bit too much will cause big changes, so I think reducing your dose by half may be too drastic.
Could it be that your feeling of being too hot might be related to your female hormones? Simple hot flashes perhaps?
Let us know what happens.