Barking dog, tips and tricks

Hi everyone!

I'm at my wits end with our 11 month old cocker spaniel. Our issue now, is his constant barking when he wakes up alone. We've been working tirelessly from the week after we got him at 9 weeks old and again from when when moved last autumn when he was 4 months old In the beginning he would bark the second we went out of the door. So we started "Door is the bore" without any real effect until we added "good bye" to it. The we increased the distance and time we were away from him. 1.5-2 months into this he could be alone for 4-5 hours without any issues, we sayd goodbye and left a sweater on the couch for him. we increased the days in a row he'd be left alone for 4-5 hours until he could do a week without issues. and then he'd be fine from when my husband left at 8 am until I got home at 2.30- 3 pm.

Now after days off after Easter he has been barking nonstop from around 11 am until I come back. Looking at cameras we have he doesn't seem scared or anything. It just looks like he wakes up, realises he is alone and begins barking his head off .

Every dog trainer we've been in contact with says that we can't reward his behaviour and must let him bark and o ly come back in when he stops. But my issue is that he will not stop, and our neighbours are complaining.

The only real change to his life is that I am very early pregnant, like a few weeks along and the fact we were home for 1.5 week because of Easter.

Do you guys have any tips how to salvage this or what to do? I'm just so upset, I don't have any time left to slowly do this whole 7-9 month process with him all over again

please help