Should I stay or should I go?

HI Paige,
I have my own issue. I' ve known this guy for four years already. We started out as roommates and eventually started talking more and sharing stuff, and little by little we built a lot of trust and became really good friends who could talk about everything. I had been getting more attracted to him, but I was afraid to mention anything, because I didnt want to lose our friendship. It meant a lot to me, because I knew I have a real friend, who would always try to give me an honest advice, and he would always give me a hand when in need or in trouble. Well, one day it turned out that he had really been attracted to me, too. So, we started having also sexual contacts, but we never committed to any kind of relationship together.I was seeing other men, he had relationships with other women. Yet, it seemed OK. With time passing by, I gradually started feeling as if he has been always better with me, helping more, being more concerned with my wellbeing, then I was with his. But I never gave this too much thought, till recently.
This year for example, when I saw him (I was away for a few months), and started living together at the same house again as roommates, I decided that it is my turn to help him in his life, so i tried to help him with his business, with housekeeping, etc, and being his friend as always. We started hanging out as well. Yet, I still dont know how, but I fell in love with him, now, after all that time. I couldnt say anything to him about my feelings initially, but evenually couldnt keep it in myself, therefore, I had to let him know. So, he became my boyfriend, because he wasn't indifferent to me either. I knew he cared a lot about me, but I didnt think he has real, deep feelings and thought that this will not really last. In fact, he's a guy who doesnt easily say "I love you". That's why I thought he is not that much into me. It took him almost half a year to relax a little bit more, and me more open with me about his feelings. Now, we are really in love, but at times, I think that we are living in kind of dream. Even though, everything looks OK, let me say a few more words about him.
He is 13 years older, he was married, now he's divorced. He has three kids (about 15) from his first love, though he never married her. She's in another country, and they have been living like that for more than 10 years. He left this woman, to marry another one, from who he has another kid. Their marriage didn't last more than a year, as there wasn't a really good fit between their characters, but he loved her. This divorce put him through a lot of pain, and it took him a few years really to recover, and get to having a friendly relation with his ex-wife. On top of it, he has two more other kids, who were not planned, they have different moms, with whom he didn't even have serious relationships, but he is not a guy who will force a woman to remove her baby. Yes, it is his fault he wasn't careful enough, and I can't excuse that part, but I understand it is not easy for him now, having six kids, from four different women, and not being divorced currently.
But to get back to our situation, when I met him, it was about a couple of years after his divorce. He was single at that time. Last year, he told me now, he liked me and wanted to get into a more serious relationship with me,but I was blind to see that, and he never took the initiative to made himself clear that he wanted more than friendship. When he didn't see the same desire in me, he gave up on the idea (he doesnt like acting first, if he is not certain about the other person's intentions, as he told me). So, at his age (almost 40), not wishing to be alone forever, he asked his first love, who was also still single, to get back together. i didnt know about that before I come to live with him again. And our feelings and relationship evolved after that anyway.
I love him, and I know he is a wonderful guy (still not perfect,but I find in him the man who I have been looking for). He also loves me. And he doesn't want to end up our relationship. But he also says he cannot end up the relationship with the other woman, even though they have not been living together for the last 10 years and more, and also have not been in a relationship for at least half that time.His explanation for acting like that is that he feels responsible, and doesn't want to hurt her a second time by leaving her for another woman (me). So his feelings tell him that he wants to be with me, and his consciousness and moral tell him that he has to stay with her.
But, he cannot really keep both, right? Making a choice seems unattainable for him, and he says that both scenarios will make him feel horrible. But I cannot put up with this situation, and even though I love him, I know that this is not fair to me, and to her. I know that I just should not have told him anything, but now it is a little bit late. Then , what should I do? I still hope that he will decide with his heart, not with his mind, cause I really don't want to lose him, and I am not that convinced he will be really happy with the other. But this waiting is killing me inside. And I don't have the strength to go on with my life and leave him either. So, if I stay, it hurts, if I go it will hurt a lot as well. I just don't know what to do. He wants me to be patient and just work on our relationship for now, but how can I bear the thought, that he keeps having another relationship in another place. What can I really expect? And especially now, when he left to go visit his kids, I know that he will be with her.And I don't like sharing my man.

If just the pure old friendship is not an option anymore, how should I act. Should I just stay and wait really? Knowing that I am not the only woman in his life, hoping that he will finally decide how to proceed. I dont want to pressure him and give him ultimatums, I dont want to make him push me away, but for how long can this go on? I understand he is confused, but so I am too. I am too much in love to see the right way, I guess. AND another important question is now, that we are not just frieds, how honest is he, I cannot say.I trust him, but I also know that he would rather lie to me, than hurt me.