When I read the first part I thought that was an odd thing to say, especially since he keeps saying it. I would say to him "why wouldn't I believe it and why do you have to keep asking if I believe you". I don't know much about the relationship (long distance-local). If (and I'm just assuming this is an if) he is long distance he might have a wife or girlfriend. You can't trust what he says if you can't see the situation with your own eyes. If he hasn't called there is definitely something wrong (hence I would start to believe he has another girlfirend or wife). Have you ever been to this persons home, seen where he lives, or any of that?
The second part of the message is what bothered me. When someone borrows money no matter how much you care about them no matter how much they borrow they should pay it back. I know you care a lot about this person, but to lend someone money is a very dangerous thing. I know from experience.
We loaned my BIL some money about 4 years ago. We helped him get out of some payday loans and I went through his budget very very carefully and spent almost 3 weeks constructing a budget for him to live on to including a separate bill for paying us back (a certain amount each month), but this budget also included some "fun money" for him - not a lot but would give him the means to go to a movie or grab a pizza once a week. Anyway...here it is 4 years later and he has only paid us back less than half of what he ows us. He keeps giving us the line "I'm good for it" "I love you guys a lot" "You know you can trust me" "I won't let you down". I keep getting these "lines" from him (and he's my BIL). My point I am saying is this is my BIL and he keeps giving me the same type of lines it sound like this person is giving you.
Please be very very cautious with this relationship and just remember, there are hundreds of other fish in the sea who you will meet and will fall in love with you and won't have to add "I hope you believe that".
So, I hate to break your heart but I think he is taking advantage of your kindness and has no intentions of anything further. If I was in your shoes I'd send this person an email ditching him, and remove the email from my contact list and have no further contact with him.
My DH's motto that he keeps instilling into me for the past 25 years.... "Trust No One".