Relationship Stress

My boyfriend and I are in love, and he has asked me to marry him.. I said yes, but we are keeping it on the down low.. No one can know but us. At least until he can afford an engagement ring and be able to ask me in public. He gave me a promise ring until he could save up enough and he said he would surprise me. But he has a past with relationships where the girls always left him because he got "emotional" about wanting to have a family, and settle down... But I love when he dose that.. It makes me feel wanted, and loved! He gets scared when he gets that way that he will spook me off, and when he dose.. He acts like he doesn't wanna be with me anymore. However he said he would never leave me because of my past too.. And I told him I won't ever leave eaither... I keep telling him.. "I'm not your past, I'm your future, and I love you.." I just don't know what to do anymore.. Dose anyone have any suggestions?? Thanks..