Well my horse isn't trained to slow down or be controled using my legs or weight and I believe that only the best horse and rider...and I mean the best can have a good ride without reigns.
Hello again. We understand that your horse isn't TRAINED to do certain things, but a lot of experienced riders (who have been in situations with horses that wouldn't stop) are telling you the same:
When he runs away with you, you CAN NOT stop him by pulling on the reins. He is stronger than you will ever be. You can have the reins on the third ring, you could change to a stronger bit, whatever... but he will STILL BE STRONGER THAN YOU.
So - accept that trying to stop him isn't the answer.
Then... he is actually just a horse, he is not a clever devious person. He isn't trying
to escape, he's just green and full of beans and probably a little anxious.
If you ride him forwards you will be safe.
If you steer him he will listen to you because he has been taught the basic aids and when he's taking off with you on top of him he's not actually thinking "ignore her", he's just not thinking at all
So when you are riding him forwards you will be able to steer him.
Look around the field and keep your eyes fixed on a big wide circle. Aim for it. Don't try to turn him really tight because that will unbalance him (and you). Ride in the biggest circle that the field will allow.
What has been said about your weight is true and it's nothing to do with the horse being trained, it's just basic physics about the horse having to deal with the weight of a human on his back.