5 yr old driving me nuts

Our 5  1/2 yr old is driving us all nuts. He has always been largely a difficult child with his behaviour and we have had to work really hard with him. Presently he has been particularly aggresive (aggressive), short temper, disobedient winging about EVERYTHING (and I mean everything). He hasn't expeienced any major changes of late that would lead to this behaviour. I am at my wits end as i am trying not to be at him all the time and jsut focus on 1-2 2of the major issues. For hitting he is going to time out for a good chunk of time, ofr other bad behaviour he has 3 stirkes in total, as soon as he loses all of these he is off to time out. We are also  tryign to give him ticks for his rare good behaviour. He does have sibblings (3.5 and 18 month old) and we  give him just him time.
I am finidng it really hard to even like my son at the moment as he has been so difficult.