I think 99% of people who fight orthodox (Jab with left) are right handed like you... And i'm SURE that every one of them felt when they started that their right was their strong hand and their left was their weak hand...
When you start your left (as it's your weak hand) will always feel slow and clumsy and pretty useless compared to your right hand, but just keep working on your jab over and over. I felt the same when I first started but seriously, after as little as a month, I couldn't even IMAGINE changing to throwing my right out as a jab...
You just get used to it, and just keep using good form with your jab and it'll get harder and faster and more accurate, trust me. EVERYONE starts off feeling like their left isn't as strong as their right. In fact in most cases your right will always be stronger, but certainly your left is your Jab hand and with some work it'll get fast and strong. Trust me!
Just keep at it and have fun...