Confusing Familys... Advice please? >.<

I can't find much on google so I thought I'd ask here...
Basically, Sorry If long post, I have only ever had two boyfriends (Aged 19) but after breaking up with my second, I went a bit wilder then I usually am lol and ended up having a 1 night stand, after doing this I realized how stupid I was being and got back together with my first boyfriend, we had always been on and off. The same week we got back together I found out I was pregnant with my 1 night stand, being totally against abortion it had to be the worst week of my life, but with long thought I thought there was no way I could get rid of it, My boyfriend was so supportive, he was more into it then I was, even though she isn't his, He wants to be her daddy and has never had second thoughts... Although I've paid for everything for her he still kisses and hugs my stomach... We're going through a very stressful patch at the moment with arguing ect... And i'm worried that when she comes he's going to change his mind... (He thinks having a baby is going to be easy, I don't speak to the father of baby, neither of us are interested in having each other in our lives)...I just need someone to talk too about it... Has anyone else been through this or something similar?... My boyfriend is trying so hard to be supportive, I grew up with a dad that was here when he wanted to be and gone when he didn't, and I really don't want that for my little girl. I'm worried that If things don't go to plan, this might confuse her when she gets older... especially If my boyfriend now decides he wants nothing to do with her in the future... I want to tell him it's all in or all out, and I think he should adopt her.. But I don't want to scare him off... baby is due is 13 weeks, some advice, even if it's truthful and hard would be awesome... xxx