Unfair treatment at work

I am five months pregnant and have been employed for six months full time as a recruitment consultant in a high-pressure environment.

My employer is not happy that I am pregnant and is putting pressure on me to 'make more money'. I have been told today (off the record, of course) that he doesn't want to 'let me go' but I must start putting in more effort and hours to make more money.

The manner in which he speaks to me is disgraceful (both alone and in front of other members of staff) and I feel like walking out. Can he get around dismissing me by saying I am not reaching my targets etc?

He is using every excuse to make me miserable. He even says that I talk about my scans too much which is nonsense - I make every effort not to talk about my pregnancy at work.