I'm really new too, but find I get a pretty good shave already. I do have quite a light growth (even though I'm not young, almost 50). I find I only need to do ATG on my jawline; and mainly on my left jawline. When you say "trying to go under the jawbone from my right ear towards my chin.." do you really mean across the length of the jawline from the ear to the chin? Or are you shaving either down the face over the jawline continuing down the neck or up the neck, over the jaw up the face? It's my understanding that generally shaving across the jaw/neck area is almost impossible (I might be wrong). I'd only go up or down (N or S) along there not E or W. I think, really, if you are getting razor burn from too much pressure and STILL not getting much of a shave maybe the razor is in fact not sharp enough? One would think if you're using so much pressure that you get burn you'd be removing hair (and maybe too much skin, too). When I started I used a VERY light pressure (more because I was petrified), and continue to do so. You say you have a strop, so I'm assuming you use it before each shave. I myself do 30 round trips on the canvas and 70 on the leather before each and every shave. I also was very mindful of not 'rolling the edge'; and I do believe this can be done in error if one doesn't really try and keep the strop taught. A strop that isn't held taught enough will sag, therefore impacting on the actual edge of the blade, and rounding it (or so I gather). All this (and I hope what I say is correct) was gathered from the forums and the Wiki (and videos), so the comments about Wiki being your friend (and also all the helpful people here) is very valid.
I'd concentrate on only ONE direction (WTG) first, and I found you DO need to very much try and use both hands (as much as you may only want to use one) and you DO need to really research and try different ways to hang the scales. I used a butter knife, envisaging where the scales would hang and even drew little diagrams and made notes. It's too hard to try the different angles when you've got a blade held to your neck; much easier with something that's not going to hurt you!