Probation and a baby

Ok so my ex and I have recently decided to reconcile. He and I have been together for five years now all together. Last year was really bad for us. I mean really bad. I won't go in to full details but short version we ended up in court for child support and domestic issues he got put on probation for a year and will be off by February 2017. Recently somehow we came back together. We have a four year old boy together.  Also we had sex one night and now I think I may be pregnant. But now he's all upset because he was told he would get off probation early and now he won't. We had been talking about getting married next year and engaged this year. But now he's saying he changed his mind. I know this sounds stupid but I dont want to be pregnant and not atleast be engaged. Not to mention the fact that he puts all the blame on me for being on probation. Though I admittedly had my part. I don't want to go through this pregnancy alone. I'm scared and not sure what to do or say to him. I've been going through all kinds of emotions, as well as he I'm sure. I guess my real question is what should I do? I feel lost help please