He's doing really well, it didn't seem to bother him too much, mostly because I think he just didn't understand. Now he understands more and he will tell me when he's upset sometimes that he misses daddy. I just hug him and tell him I do too and it's perfectly ok to miss him. I made a photo book of pictures of his dad. I explained all the pictures to him when it came. I plan to continue to talk about him and remind my son that his daddy loved him more than anything in this world. I'm just worried that it will get harder as he gets older and sees all of his friends have dads but he doesn't. Though nowadays there are plenty of single moms out there so maybe it won't be that bad.

Thanks for your replies everyone. I'm so glad I can share here even though this stuff doesn't really have to do with bipolar. You are all my friends.