Short answer: Yes, you can, but it's not really any easier than starting from the ground up and building a new character.

Long answer: While fourth editon D&D shares many setting conceits with 3.5 and earlier editions, the two are very different games in terms of how characters are constructed and the way challenges are addressed during play.

You might want to check out this question about the differences between the two games for a general overview. The accepted answer is pretty good.

So, about converting your character to 3.5... Well, it depends on exactly what you've built, but since 3.5rd and 4th edition make reasonably similar assumptions about setting, it shouldn't be too hard to convert your character's concept across.

However, as you may have noticed, there are a lot of differences between 4th edition and 3.5, most notably including different scales of leveling and a differing level of combat-centric-ness that will likely make it impossible to convert your character without making compromises.

As far as I know, there's no formal downgrade migration path available, so you'll have to do the conversion the old-fashioned way: Hit the 3.5 books and try to work out how your character would fit the system.

Unfortunately, I can't give you more specific advice than that without knowing more about your character. Could you possibly post your character sheet?

Short answer: Yes, you can, but it's not really any easier than starting from the ground up and building a new character.

Long answer: While fourth editon D&D shares many setting conceits with 3.5 and earlier editions, the two are very different games in terms of how characters are constructed and the way challenges are addressed during play.

You might want to check out this question about the differences between the two games for a general overview. The accepted answer is pretty good.

So, about converting your character to 3.5... Well, it depends on exactly what you've built, but since 3.5rd and 4th edition make reasonably similar assumptions about setting, it shouldn't be too hard to convert your character's concept across.

However, as you may have noticed, there are a lot of differences between 4th edition and 3.5, most notably including different scales of leveling and a differing level of combat-centric-ness that will likely make it impossible to convert your character without making compromises.

As far as I know, there's no formal downgrade migration path available, so you'll have to do the conversion the old-fashioned way: Hit the 3.5 books and try to work out how your character would fit the system.

Unfortunately, I can't give you more specific advice than that without knowing more about your character. Could you possibly post your character sheet?