Don't love my fiance anymore

My fiance and I have a one year old son and are expecting another in early june. I do not love this man anymore I wish he would leave me. I feel so trapped everything he does annoys me so bad I can't even stand to look at him. I am starting to hate him so much. I don't know what to do I have a good job that I can return to after my maternity leave. But how do I go about splitting up. He already told me he would make it hard for me to leave but I don't want to be with him anymore at all. I don't even want him there for the birth of the baby. Please help I qm struggling I qm so unhappy with him. I feel so trapped he is so controlling and bossy he thinks we have to be together every waking minute he is suffocating me