Don't lose hope! You've only been working on this for 2 *days* (that's only 48 hours) - he's been trained to pee in his diaper for the last 2 YEARS (years = many, many, many hours). It's what he is used to (peeing in the pants, not on the potty), so please don't get frustrated with him. He's trying to learn!
The best thing I can think of to keep yourself in a good mindset and keep both of you relaxed, with the goal of learning in mind: think of how your son learned to walk. Did he do it all at once? Never a bobble, a fall, a misstep? Of course not! It took him some time to learn to stand without assistance, to get his balance, to take those first few steps, then to take more steps in a row, etc. *This* is what potty training is like. Please be gentle with yourself (set realistic expectations) and with your son (remember, he's NOT doing this because he "doesn't care").
You guys can absolutely do this - be a team, help him learn his body's signals that he has to pee/poop (pressure in his bottom, antsy-ness, etc.) and then increase his chances for success (keep little plastic potties in every room). When an accident occurs, remain calm and cool and matter-of-factly clean it up together as a team, throw the undies and pants in the wash together, wipe up the floor together, talk about how next time, it's more comfortable for him to go in the potty. Make potty visits together - you on the adult toilet, him on a little potty.
It's totally do-able. It's just that our culture seems to think that kids will train themselves if we just wait long enough (uh, right!). Did you know that in other countries and cultures (and in our own 100 yrs ago), babies are using the potty reliably by 18 months? This is NOT to put pressure on you AT ALL - it is NOT a race - it's just to tell you that the vast majority of babies & toddlers are capable of learning to use the potty *before* age 2. While I'm sure some kids do "train themselves" (a small percentage), most do not (how many moms are posting to boards with 3 & 4 yr olds who still need a diaper to poop in because they don't want to use the toilet --> lots!). The physiological truth is that kids are capable of being toilet independent *much* earlier as long as we parents look at learning how to use the toilet as a *process* that requires teamwork and patience (remember, it's like learning how to walk, or learning how to eat neatly using your own fork and spoon).
Potty training can be a wonderful way to really connect with your child! If you really want to do it as a family, you can even gently potty your 4-month old (I bet you know "the poop face" already!) and avoid cleaning up those ungodly messy blowout poops. Here are some tips that apply to babies AND toddlers - hope it gives you some useful ideas!
http://www.viviente.com/2005/10/how_to_do_parttime_pottyt...