Wow, you sound so much like me! First of all I'm so sorry that you have to go through this, I know how much it stinks! I also have Harm OCD, yet it revolves around hurting myself, and it does result in "I want to" thoughts, such as "I want to die" when I seriously have no desire to die! This is what OCD does, it'll try it's absolute best to scare the living daylight out of you. Since the last thing you would ever want to do is hurt your son, that's the topic that it's going to latch onto!
My CBT specialist recently told me a metaphor that really helped me out: Think of these thoughts as annoying kids on the back of the bus, and you're the bus driver. They'll repeatedly jokingly tell you to crash the bus, which is the last thing you'd ever want to do, as you'd be hurting so many people. You don't listen to these kids though, you just continue to drive the bus to its destination. The moral of this is that you need to continue to drive your figurative bus, as these thoughts can taunt you all you want, but they will never lead to anything, and they can never make you do anything. Also, it may help to try your best to return to your life (I know how hard it is, I missed school on and off for 4 weeks due to my OCD and it was very difficult to get back on track), as when you engage in your normal activities once again, you'll notice that your thoughts will fade! Also, try not to prevent these thoughts, my therapist constantly told me that it's very important to just let the thoughts come, and heck, maybe even encourage them, because A) trying to suppress them will only make them worse and B)the more you encourage them, you'll notice that they are just thoughts and that they have no power over you- I know how crazy that seems, but it has seriously worked for me!
I hope I could provide a little help, as I'm nowhere near a parent, I'm actually just a high school student, but I can imagine how torturous that must be! Best of luck! :)