It is hard to find the balance between love and discipline. Taking school out of the equation, how do the 2 of you interact the rest of the day? I am saying this because I think as moms we often relate better to one child of ours than another, certainly throughout different stages of life, while perhaps another child of ours can seem to just push our buttons.

Would you say he's in a button-pushing kind of stage with you? I say this because I have gone through this more with one particular child of ours, but also with each one of our dc in different stages of their lives. This is a tough rut to get out of, but get out of it one must.
First of all, I'd spend some time really being watchful and mindful of what's going on in the day, and even jotting notes about it. In the heat of the moment, we can lose site of what the entire day was like. Boys, especially, don't like for things to be drawn out or go long. I'd print off the suggested times for doing boxes in LHFHG and write next to them how long it's taking him to do each of them:
Approximate Times for boxes in LHFHG...
Left side of plans:
Reading about History: 10 minutes
Rhymes in Motion: 5 minutes
Rotating Bottom left box (Science, Art, Dramatic Play, Thinking Games): 10-15 minutes
Bible Study: 10 minutes (add an additional 5-10 minutes on Devotional days)
Corresponding Music: 5 minutes
Right Side of Plans:
Fine Motor Skills: 5-10 minutes
Phonics: 15 minutes
Storytime: 10 minutes
Math: 10-15 minutes
I'd also jot general notes pertinent to how things went. For instance, you may notice he wakes up happy, or maybe he wakes up not so happy - maybe an adjustment in the start of school would be good. You may see math just goes on and on and sends him into fits - maybe setting a timer for 20 minutes and stopping when it rings would help. Or maybe you may notice that when there are too many interruptions he loses focus and gets angry about having to stop-start- to come back to do school - maybe you choose a quieter place for him to work, or maybe you make sure not to answer the phone and get side-tracked when homeschooling (a lesson I've had to learn multiple times

). You may notice he's testing you, starting off slightly negative with comments to see what you do, and then getting really negative as he pushes the line further and further - maybe you and your dh need to have a set consequence for this. Or maybe he loves reading, and that part goes smoothly - hooray, celebrate that! Maybe writing is frustrating for him, and he needs you to lovingly sit near him and be a real encourager to him during that time. Anyway, if you could do this, and share your notes with us here, we can help come up with ideas to tackle whatever things necessary, and we can also celebrate what's going right with you here!!!
I know it is hard sometime, but I'd endeavor not to raise your voice to get him to do things, but to instead, to be very calm. Oh do I know this can be hard! But, that rise out of us is sometimes just the attention they were wanting, so we are in fact rewarding them for their behavior by doing so. Also, I've had to work hard on having a healthy, close relationship with one of my ds more than the others, and if you recognize that, it's important to think how you can accomplish that. My ds needed a lot of extra hugs, sincere compliments when he was doing things right, appropriate and well-explained expectations, and consistent, calm discipline when he misbehaved. This was/is a challenge, but now I'd say I'm struggling more with one of our other dc, and things are going awesome with this one. So, I just want to encourage you that you have the opportunity here to really work to hold on to your son's heart - an opportunity made more difficult and sometimes near impossible to do - when dc are in ps. Mind you these struggles don't go away with dc in ps, so one other thing my dh and I decided never to do anymore was "threaten ps". We sat down and decided why we were homeschooling and shared that with our dc. If you haven't done that yet, and I'm sure you haven't as you've just started, you may want to do that. It gives my dh and I resolve through the harder times of homeschooling to "press on to the goal and win the prize for which God has called me".

I am praying for you, but I want to encourage you that this can be fixed, and you can enjoy homeschooling your dc. HOD is simply the best thing out there because it works on not only the "head" but the "heart". HTH - and I'll be checking back!
In Christ,
Julie