This can be a sticky situation depending on how long you have been together. If this is a new relationship, under no circumstances should you be loaning or giving him money. If you have been in the relationship for a while, things do come up, especially if you are younger and still trying to get your finances together.
If you continue to give or loan him money, you become an enabler, because he knows that he can depend on you, so he is less likely to manage the money that he does have well.
Here’s my question. If you don’t give him the money, what will happen? Most likely, he will ask someone else, so let him do that. You can’t drain your finances to help him. You have to take care of your financial commitments first. See if you can help him in other ways instead of giving or loaning him money.