I agree with everyone else.
He's telling you the truth, so believe him.
However, whether or not you should move on depends on the circumstances.
My best friend has been with her boyfriend for about 8 years. Most women would have been like "Eight years?? What the hell???"
But here's their situation - they met when she was 19 years old. If they had dated for 2 or 3 years and then gotten married, it would have been a DISASTER! Out of college, NEITHER of them knew what they wanted to do. She's only been in a stable job that she wants to move forward in for the past 3 years and he's only just now finding the right field for him.
They're getting married this fall.
So if you're dealing with THAT kind of situation, then I'd say, don't fret. Him wanting to wait to marry until he's stable is actually a SMART move.
But if we're talking about someone in their late 20s to early 30s (or older), then we're talking about a different situation. Generally speaking, men should have some kind of stability by this time. But many times, many of them do not for various reasons.
I think the only reason for you to stick around if this is the case is if he's unstable with his job and has only just found what could potentially be his niche. Some guys don't want to take that leap until they feel they can be a good provider.
However, outside of that, if you know you're stable, you should just move on my dear