He is as responsible as you for the pregnancy.
dont't waste another minute of your time on this man. He is an absolutely irresponsible and unfeeling scoundrel. He cheated on you, lied and treated you as if you were worthless. Though you feel so alone you are probably better off without this man in your life. The only thing you are guilty of is that you were na´ve and too trusting and I am sure you have learnt valuable lessons from this experience.
No one can force you to have an abortion. It is your body and no one can dictate to you what you should do. You have not't messed up your life. You have made a mistake. Yes, it will be different if you keep the baby but you will manage and you will get through this.
You are not worthless because you made a mistake. Your boyfriend has made you feel this way. He is a coward who cannot stand up to his responsibility.
But if you are still unsure about your decision, speak to a counsellor. It won't be easy getting through this and you need support from someone who will listen and not to condemn you. If you need a counsellor I can recommend you, do PM me. The counsellor can help in coming to terms with the guilt and grief you are suffering. You need to forgive yourself so that you can start living your life again.
Make as best of a path as you can and feel proud of getting through all challenges big or small... Focus on matter that will improve your situation and forgive yourself, love yourself more and more each day... Grow through the hard times and feel proud and glow as a strong woman... I know you will. My heart is with you...