How do I tell my ex I'm pregnant?

We broke up last week because he thinks I was cheating on him (which I was not) and I just found out that I'm pregnant the other day. I don't know what to do! I'm scared he's not going to believe it's his and I want him to be a part of the baby's life but I'm not sure he's ready to be a dad yet we have a weird relationship. Even though we're broken up were still best friends and We went to dinner in the city and I slept at his house last night (different beds) were together almost every day and I don't know how long I can hide it from him, last night he was asking me why I wouldn't have a beer with him and he seemed sketched out and I think he has a feeling but I don't know what to do