Is this an awful thing to do? Or should I think of myself first?

[Minimim]

Would I be unreasonable (and a horrible person!) to leave a job I detest for my perfect job, while still in my probation, just after my boss has announced her pregnancy and is expecting me to cover her mat leave?

There is nobody but me to cover within the company and I know that having to recruit someone will be very hard due to the location and specialist area, so will put her under a lot of stress.

But... I'm miserable. If I stay for the mat leave cover that's at least another 14 months in a job that is making me hugely depressed after just two - the thought fills me with horror! And actually a very large part of the reason I hate the job is my boss's shitty attitude towards me.

I feel like I shouldn't even be thinking of not quitting but the guilt at putting a pregnant woman through loads of stress (and it will definitely fall to her to recruit/get a secondee/'sort the problem' as her boss will not take any responsibility for this). I know that she'll be completely shocked at me leaving...

Help?!

The fact that it's knocked your confidence in two months is worrying. A toxic work environment can be really damaging, and that damage can last for a long time.

I'd get out if I were you.

Op, sounds like we have worked from bosses cut from the same mould ( my ex boss once rang up to bollock me because her friend a colleague had royally screwed up doing a task that I had nothing to do with as I " should have noticed" ( . was on a/l when the screw up was made. In another country) . One of many shitty reasons she used too keep me in my place. Oh and telling me on my way into an interview for another position within the company " I've told them not to give it to you" . Nice. I lasted years but ended up with anxiety and depression and after finally leaving it's taken 18 months to get back to my true self.
Leave and go to your perfect job, it's not your responsibility to cover her mat leave.

You're a very nice person to even be worrying about this. Go for dream job of course.

A job is a contract. Your employers don't owe you (and won't give you) any more consideration than the terms of their contract with you. You don't owe them any more than the terms of your contract with them. The fact your boss is now pregnant doesn't make you more responsible or more liable, she is exercising her rights under her contract, just as you can too. Guilt shouldn't come into it. Take the new job with a clean conscience!

its 14 months

No, it's 14 months plus however long it takes for another dream job to come along and be offered to you.

Go, go, go!!!!