I have been dating this man for 6 years, I have 2 children(not his) and he has always been there for all of us. We have had are fair share of issues, but for the last year we have been at our best, I've been in school since January and he had been doing more then normal because of that. Also, I seem to be doing nothing but studying and would notice when he whould make comments like "it's friday night and were not doing anything". Then 2 days before my birthday --I had a very hard test in school & was crunched for time when I got home, so when He tried to give me money for bills and it wasn't all of it I stated "I wish I could pick and choose when and what bills to pay" but then I said you know what never mind its not a big deal I'm just stressed out, but whithin 10min he was telling me that -- he no longer wanted to be with me that tiny argument was the icing on the cake. I just don't understand we were at are best, we were really getting along and functioning not only as a couple but a team. And then (boom)like getting hit by a truck its over, it has only been 2 weeks- and we did talk twice- he states that when he's with me he's happy, but when he's not he only thinks of all the wrong I've ever done to him (all the way back to our first year of dating). I know that he has done wrong too but I forgave him and I don't rehash all that drama, of course I am in pain, and I am not calling him because it hurts so bad. I guess my question is what can I do to save our relationship?(I have apoligized many times already for my behavior) I do love this man with all of my heart and its real devastating not to have him around. Please any advice would be appreciated

Are you sure this man has not found someone else. There are 2 reasons I ask this. 1. It is very rare for a man to leave his woman and generally this only occurs when another woman steals him away. 2. often when a women becomes over preoccupied in something such as work or study and doesn't give her man enough time and attention, generally he will surcome to almost any woman willing to fill that void for him.
Im not saying that this is the case with him but its something you need to confirm before doing anything else because it impacts on what course of action you need to take next.
If it turns out there's someone else, then you will need to decide if you want to compete for the heart of a man who is willing to walk out on you when the going gets tough rather than work through things.
If there is no other woman, you still need to decide whether or not you want a man who walks away from you when things aren't going his way. If you do! I recommend putting your apologies aside and asking him what it is he needs in the relationship and talking to him about how you can both make the relationship more satisfying.

Thank you for your advice, fortunate for me I do know that there is no one else (at this time) any other advice or information I do appreciate hearing right know as my world (too me) has been flipped upside down