It shouldn't matter at all should it!
I don't know for certain which I am.
When it comes to writing, I always use my left hand.
For things like knitting, using cutlery or a can-opener, I am right-handed.
When decorating, I swap the paintbrush from one hand to the other, depending on the angle of the thing I am painting.
I grew up doing almost everything else with my left hand, but as an adult have changed to doing some of them, such as playing racquet sports, with my right hand!
The thing is, I fell and injured my right arm very badly when I was only two-and-a-half years old. Apparently, even after the plaster, and then the sling, were removed, I simply wouldn't use it for about six months, so did absolutely everything with my left hand.
However, my mum says that I was showing clear signs of being left-handed before the accident, which makes it all the more odd that I have changed to doing so much more with my right hand as an adult! 
In school, I only ever had one teacher who tried to make me write with my right hand (when I was six), but the results must have been bad enough to convince her that it wasn't worth the effort, as she only made me try the once!