probably you were compelled to write with your right hand at school.try writing a page with your left hand everyday.by the time you are finished with one notebook you would be perfect.. i dont know if it is scientific but i ( left handed) trained myself to write with my right hand using the same method

I, too, am a mix-handed person almost exactly the way you describe, but I do a few other things right handed in addition to writing-- bat, throw, cut, use a hammer or screwdriver, but I play tennis mixed (no backhand unless under duress), but ping-pong only left-handed. I eat European style--fork in the left and knife in the right. I can paint ambidextrously and similar things like beat mixes when cooking and so on. In the army, I fired my weapon right handed. I really don't think that the person's answer about being taught right-handedness in school for writing is correct as that practice was stopped long ago (I am a retired teacher). My father suffered that particular indignity and he stuttered as a result his entire life. (His left hand was tied behind him as the nuns considered left-handedness a sin.) I can write simutaneously left and right handed, but the left is like a mirror image. My childre are all right handed except one boy who is totally left handed except that he taught himself to be a right-handed drum major. I was, too, a right handed drum major! I have been puzzled all my life about which is my dominate side, and I am most happy to know that others also wonder. Perhaps we are just as God made us!