I know you have a new baby too, so that’s not good for your family either. @chinchin31, this happened to me when I took this job. I really wanted the job but the workload they imposed on me in one part of my job meant I couldn’t fulfil my contractual requirements in the two other parts. So I spoke to my boss. He ignored me and made excuses. So I started putting it in writing. This gave me evidence to show I’d challenged the inequality I was facing when the end of my probationary period arrived. I also logged everything I did so I could provide evidence of the ridiculous amount of work they’d given me.
Are you still on probation? Why are you having to do so much overtime? Start writing down what you’re having to do and why it’s taking more than your set hours. Is this overtime paid or unpaid? And go back over your contract and look for evidence of what you were contracted to do and how that compares to what you are having to do.
What sort of work are you doing? Are there plenty of other jobs for you to go after? Is this standard practice for your field? The reality is, if there aren’t many jobs in your field, you might find the same would be true if you changed jobs (that was my situation), so you might be better trying to fix things here rather than ‘jumping from the frying pan into the fire’ as they say. I’m not sure of your situation though.