I have a jack russel cross beagel , he is 14 months old.

I have had him since he was 8 weeks and he was very easy to house train, he did have a destructive side when it came to my underwear and shoes and still does if he is left at home. I very rarely leave them unattended and I do have another dog who is impeccably mannered, never makes a mess to keep him company whom I have had 2 years longer than my Jack russel.

I have recently had a baby (if this will upset him)

He is now getting to the state where I am lost as what to do with him, he urinates everywhere while I am asleep, up the doors, against the sofa, TV he has made a mess under my baby's cot since she has been born. (even if I leave the dog flap open over night) if I leave him unattended he destroys everything and anything in his sight.
It has got so so much worse since I was 36 weeks pregnant till now.

I do not want to rehome him as everyone tells me I should as I love him dearly but I need to stop this as my house and my things are being destroyed.

Please help!!

IS he neutered... if not get that done asap.

Yes he is already castrated..

He's marking territory, so I would say that he is definitely not happy with the new addition to the family. Have you changed your routine dramatically since the baby arrived? If you have, then I think that you need to get back on the old schedule as much as you can. You might also want to try a DAP diffuser, and crate if your dog was used to that before the baby.

The only thing that is different is I had an emergency c section and have not been able to walk them like I did before, my partner now walks them do you think that is enough to upset him. I guess its just the whole not getting as much attention? You think?

Yes. Dogs are creatures of habit. And now the routine has drastically changed. Some dogs take it in stride and others show their displeasure.

He also may feel that his position in the family is changing and may need more leadership then he is currently getting.

As a note, just because a dog is not neutered does not mean they will urinate on everything. I have seen just as many neutered males ( and they were neutered as young dogs anywhere from 4 - 9 months) mark on everything. I have 4 intact males living with me and they do not mark in the house. Ever.

Jaime