Morning.
In my experience the commentary "I am having trouble with LBW's" is 99% of the time is frequently mentioned in the same paragraph as "I trigger back and across".
That is not to say the trigger is at fault but more it can be a symptom. The commentary from Mr Cricket should be helpful - as far back as 1936 Douglas Jardine talks about leading with your head as "the topple", effectively leading with you eyes causes you to topple your front leg onto the line of the ball.
In your post, the first thing that you are concerned with is where you stand and what your stance is. It is a modern fad that batsman are encouraged to stand with a wide base and then trigger. Personally I see people trying it, but it totally over complicates batting - just ask KP. Which is what I think has happened to you.
Your stance should be comfortable and relaxed, a trigger is used to release the tension and help your feet move against fast bowling, unless you are playing Div1 or Premiership standard, I think it is unlikely you are facing anyone fast enough to make it worth triggering. Look how still and balanced Michael Clarke or Matt Prior or Eoin Morgan are at the crease - or if you must have a trigger, see how Bell and Trott play, they are very relaxed and natural at the crease and their trigger takes them into the right position, rather than moving them away from the right position, which is the classic fault of an amateur cricketer.
The key is the position you are standing when the ball is released, which must be still, trigger or not. To get this right work backwards from where you need to be at the moment of release. Your right eye (if you are right handed) should be over off stump - you might need to spend some time in front of the mirror to get this right - so work out where your trigger takes you and take a guard which leaves you able to finish in the right place. By being in the right place at the start, you are minimising the risk of being trapped on the crease.
Can you be open chested or closed chested? either can work, but if you are unsure, standing side on is usually a good place to start and typically being slightly open is more comfortable. Your key problem should be to stop triggering into a position which leaves you vulnerable, get your head (and subsequently your feet) into a good position at the start, then you can your on the exercises that Mr Cricket mentions - also having someone underarm flat tennis balls at you is also a good way to work the front foot shots.
Hope that helps
p.s. I would warmly encourage you to ditch the trigger!!