I can also totally relate.
My ds3 is 4 and he is very erm challenging . The meltdowns, tantrums, hitting, swearing - just a world apart from my other 2 dss. Can't believe in your OP you saying people putting blame for it on you. I would swing for anyone who intimated that to me. I am not perfect. I feel like a crap mother. Frequently. Different personalities & all that. Ds3 was the easiest baby ever. He was very much wanted, adored. Dh found him very difficult when he became a toddler. I didn't. We had a hellish year or 2 as they locked horns. Now however, he is 4 and he just pshes my buttons in a way I've never experienced in my 8.5 years of motherhood.
I've read a few times in anger management about using eg traffic light system for recongnising your stress/annoyance/anger rising. Trouble with ds3 is I go from cool to red in an instant with him sometimes. He just presses that button...
I do suspect that there's more to it. He is just extreme. I started a thread just this last week, it's a shock after 3 boys to suddenly find 1 to be so challenging. I really wish you well. and hope you get some coping strategies in place - I'm still learning/searching. ANd cling onto the fact it will get better. Sooner rather than later hopefully.