Is he in love with me or not?

I am in love with my bestfriend. We were headed into a relationship ,but at the last moment he froze up,because I just got out of an abusive relationship in November and just found out I am pregnant from that relationship ( I was 5 months and had no symptoms of pregnancy at all and found out incidentally) . Then later on after that (about a month ) he went back into a relationship with his ex from like 4 years ago. Problem is he treats me like his girlfriend instead of her. We are on the phone all day and night. When he is not at work, he hangs out with my family and me and never goes home. She doesnt call him much and when she does he always tells her that he is with me. They hardly hang out . He takes me out, kisses me,goes out of his way to make sure I have everything I need,goes to dr appts and etc, plays with my son like he is his son. We spend time with both his friends and family and mine. He gets mad when I mention his gf's existence.He keeps assuring me that he isnt going anywhere and he makes plans for us in the future. He has been there for me through every traumatic thing that has happened to me and even took me to the hospital when I found out I was pregnant after he worked a double. I want to know if he is in love with me and why did he enter back into a relationship with his ex? Oh yeah btw, I dont think it matters but I'm including it anyways he is a Sagittarius and maybe that will help out with some of the answers.