Why is my horse doing this!?

so today when i was riding her she was shaking like crazy and wouldn't let me get on her. finally i got on her and she was fine till i started trotting her all she wanted to do is run everytime i would tell her slow and pull back a little she would toss her head stop and jump (not quiet rearing) finally i got her to stop she was still shaking idk why. then i went into a lope she wouldn't lope at all she wanted to do is gallop. i got her from an auction totally messed up i spent 4 months training her as this problem happened before. anyways, i finally got her into a lope and kept her calm. she was fine. then i decided to do barrels but slow at a trot lope. i went to the 1st barrel no problem after turning it she went into a full speed gallop and i wasn't expecting it. i almost fell off. i got her to go slow and she has never taken off before. she kept doing after each turn. even if i walked to and around the barrel. any reason why she did this today?