After 7 years of heartbreak how to i still love him?

I met my ex at 15 and i feel for him big, i fell pregnant within 6 months in but we were both happy, until ppl started putting ideas into his head of how he was going to miss out on his dream career, but i didn't stop him in fact he joined the army a month before i was due to give birth, even though it broke my heart to do it alone, i didn't want to stand in his way, even when he didn't turn up when my son was very ill in hospital at 6 weeks old so i kicked him to the kerb hoping he would realize what he had lost and fight for us but he didnt and we lost touch, we have been back in contact for 4 years now and i know he is the only one i could ever love the way i do but he doesn't see it all the time, but every now and then things he says or they way he does certain things leave me wondering if he is living his life and waiting to commit later but i don't want to wait around forever. he has been married it lasted 2 years. It feels like he is keeping me as back up but he won't tell me honestly how he feels or nothing. His mum has never seen her grandson and according to my ex she doesn't want to. he has seen my son several times in 6 year yes about once a year although to me it is better than nothing but i want my son to have more. i don't even know if he truly cares about him 1 birthday card in 6 years nothing else but he pays csa. I guess i just want him to either be honest about how he feels and let me get over him or love me 1/2 of what i love him. I don't know why i do i guess i don't want to upset him incase it backfires on my son. But it does anger me that he gets to have fancy holidays nights out partying having fun etc and i put everything i have into raising my son. I am not your typical teenage mother i have my diploma and i give my son the very best i possibly can and i don't regret him and he wasn't an accident or a mistake, my current partner works and raise's my son as his own and he is fab for doing that and dealing with the fact i can't fully love him. yes he knows. Its like a triangle my partner loves me the way i love my ex but they way i want my ex to love me. I just feel like there is not enough chemistry between us but there is between my ex and i. I am so messed up and i am tired of getting my heart broke every time and still loving him and still willing to lay my life on the line to protect him and give him my all. Seriously is there anyone that could help me understand this or a way of dealing with it? or even explain how it is possible?. or any guys who could shed light on why he keeps me hanging on? thanks