If he is willing to work on the issues, then it may be worth trying to mend things first before you decide that you want to move on. Think about what would be a realistic time frame during which you want to see some improvement in the relationship? Do you want to wait until the baby is born, do you want to be more flexible, etc.
Your patience would be reinforced if he shows some effort on his part. The two of you may decide on how you want to address these issues. Figure out what is causing the most friction to the least friction ex: money issues, responsibilities, fidelity, having grown apart, miscommunication, etc. Then, you would want to make some short and long term goals for the relationship that meet your mutual needs and wants.
Couple's therapy or working with a couple's coach are some options and there are also self help tools available (although, it is recommended that some professional help is sought out first).
Recovery of Your Inner Child: The Highly Acclaimed Method for Liberating Your Inner Self (Paperback)
Couple's Communication Made Easy (Audio CD )