Hey Andy

The jab issue sounds like a technique problem. Straight shots are the most economic to throw (the fastest and most efficient way from point A to point B is a straight line). Check out this article on how to throw a boxing jab, then get in front of a mirror and do some self analysis;
  • Are either of your hands dropping before/as the shot is thrown?
  • Is your elbow 'flaring' to your left as the shot goes?
  • Are you throwing your weight forward with the shot (check this out by examining your stance side view or 'in profile'). This shouldn't happen for 2 reasons 1) the risk of getting punched in the face and adding your weight to your opponent's and 2) the shot becomes dreadfully inefficient and unnecessarily tiring.
  • Again, the jab should be an effortless shot, a shot that we can always rely on no matter at what point of the contest we ar ein or how tired we are.
In terms of bagwork' 'Theme' your rounds. E.g. Round 1, all long range, plenty of foot movement. Round 2, go for short range, big body shots (I'm gonna be JC Chavez in this round!) etc. Mimic the style of your favourite boxers. If there's any posters in the gym, have a little read of them in between rounds, this will give you a lift for the first few seconds of the next round.

Does this go some way to answering your question?

Cheers

Fran