Thank you all for all your support and advice, it's nice to know that other people are having similar issues and emotions.
I feel a bit less like a crazy lady now lol.
We've had a better time over the last few days - I've been trying to avoid the kind of situations that cause stress and tanties (not always possible because there are some things I just have to do) and to get as much done as possible in the morning while Yasin is at his best so that in the late morning and afternoon when he is more stroppy we can have more down time.
DH is home soon - I can't wait to get a few hours off.

Christy, defiant weeing sounds like a hard one to cope with. Pete did really well to walk away. I'm hoping that TT will click in the next few months so that we don't have to TT in winter.

TaffyLou, I got a new monkey back-pack/harness this week. We had one previously but I lost it. Suprisingly he has been quite good with it - I expected a big tanty but once he realised that he could bolt but only so far he's pretty good about it. I think it's improved things a bit by reducing my stress levels when we're out and about.

Sherie, I do think that I'm feeling more pressured because I don't have anyone to de-breif to at the end of each day. I'm terrible on the phone. I geuss I need to work on that.

deejoy, I like the idea of DH putting the undies on. I might see if we have more luck if he gets dressed with DH when he gets back. They often shower together so it's just a progression to dress together too.

Kellie, I've spoken to his childcare center because he has regressed there as well (he used to be happy to be dropped off in the morning but now he cries) and they said that once he's over his morning tanty he's fitting in ok - doing all the activities, eating, napping and so on. I didn't think to ask if he was behaving normally for his age butr I geuss they would have said something if he wasn't.
I like the star chart idea. We had one but then he pulled it down and I never made a new one - maybe I've regressed lol.

Marydean, do you contact the behaviour support throughh your MCN? I don't have a relationship with our current one. She annoyed me the first time I met her so I've never been back. Maybe I should check in and see if there is another one there.

Caro, thanks for the support, my DH makes similar comments to yours if he has to look after the boys on his own for a few hours.

Melanie, it must be hard to deal with the poo, you have my sympathy. I think you're right that I should be more aware of triggers because then I can try to modify situations/adapt my own behaviour a bit to reduce the stress for all of us.

melbee, my hat goes off to you. It's tough being a single parent. I hope you can find some child-care soon so you get a break. Lets just hope this age and stage pass soon lol.