I was told I couldn’t have both a career and a baby

I had to tell my employer I was pregnant at 8 weeks due to morning sickness. I work for a small company with only 5 employees. On telling my employer I was pregnant the first question I was asked was ‘was it planned?’ And I was told I couldn’t have both a career and a baby. I decided to take maternity leave as soon as allowed as I was put under severe stress to get work done before I went on leave. I was asked how long I would be off for and when I said 12 months I was told I was leaving them in the lurch. I wasn’t allowed to take any holiday before I went on maternity leave and a full year of holidays would be paid at the end of my leave.
I had a meeting to go back to work part time and this was agreed followed by a formal letter to say it was only now agreed for 3 months. On returning to work I had no back to work meeting despite receiving an e mail a week before to tell me my job description had changed and I had a new contract of employment. On returning to work I was sat in a separate room on my own, had no phone, the software I needed to do part of my job ( I’m a chartered accountant) had been removed from my computer and the majority of clients I acted for before were taken off me. On top of this someone with the same job was promoted over me the week after I returned. I feel like I am being pushed out and if I don’t leave within three months I will be told I will have to go full time. Having a baby doesn’t mean you can’t do your job!