My Horse Pulls Away From The Bit When I Try To Stop Him. What Do I Do To Stop Him From Doing That?

Your horse pulls at the bit because you are letting him get away with it. You need to be firm but not aggressive to stop him from behaving like that. When you ask your horse to stop ask for his head as well. Have a short rein and rather than just pull (which is probably causing him to rear) tug down. Have your hands closer to either side of his wither. When he arches his neck and stops, release the pressure as a reward. Do some exercises with him in an arena or large yard, stopping him like described above at walks, trots and a canter. Do some turning exercises too. Your posture could also be a reason too. Before you ask him to stop, put your bum right into the saddle, keep your heels deep and lean back slightly. The bit you are using may also be a problem. It could be hurting him. See your saddler and tell them your problem and ask for a different bit. Maybe a slightly thick egg butt snaffle that's also sweet iron.

I'm sorry but I was angry at your responses, first you need to get his teeth and back checked, secondly it has nothing to do with food and thirdly it's not because you're letting him get away with it.
If teeth and back are fine then it might be that you're too heavy handed, the horse's mouth is very sensitive and you should only need a tiny amount of pressure to halt. This is only done through lots of transitions, but don't pull and pull until he stops you need to give and take, (squeeze like a sponge and relax, keep doing this till he stops) when he has stopped give the reins so he feels the pressure has been taken off, that is the reward you will offer. The more you do this the quitter the squeezes will need to be. I just have to squeeze very gently for my horse to stop and she was just the same. The most important thing is to not lock your hands, by doing this your horse is responding by fighting you by throwing his head around, if you give the rein he has nothing to fight against and will start trusting your hands. It takes time but by doing 10 mins of halting transitions at the beginning of each session you will get there.
The rearing up could be due to bad fitting tack or again that it's his way of fighting you, you don't say how old he is, the most common cause of this other than tack is heavy hands, so relax the hands and make sure you allow him to go forward and not blocking him, if he still rears up then I've often found that cracking an egg on the poll helps as they think they have hit their head on something. But this is not the solution as if the ground work has been done properly he wouldn't do it. Take it easy and stay safe but I advise you to get the teeth and back checked first

Tigger85 has a good answer for you. Problems like this arise from training (horse and/or rider), improper tack, or physical problem. It sounds like it would be worth the investment for you to hire a trainer to help you go through the checklist and find out exactly which is the problem. You will also find better help on a website or chatroom specifically for horsemen.

You may be pulling to hard on the bit; causing the horse to pull on the rein to avoid pressure, and show to you that you are pulling to hard. Try to do half halts, by pulling and releasing on the rein. However, make sure you don't drop the bit in the horses mouth, it will make it worse. Also use your seat to help stop the horse, by squeezing your knees on, and keeping you thighs on the saddle. As well as using your seat by sitting to the trot or canter and using a restraining seat aid to go back in to the walk or trot. I'm not sure if it will work for you, but it worked for me and my 2nd level dressage horse when I first bought her.

Put a running martingale on him and it will stop him putting his head up.

If he rears up then be determent and kick him on.

Well to stop him rearing you give him a kick when he is in the air everytime he does that and then when he gets the message then you stop!!! And if that doesn't work then I have no idea but I should work