swelp me?

It looks to me as though someone were writing the patois of a speaker of the American language as it would sound, rather than in the words from which it derives. I would say, "swelp me," stands for "so help me," which is an intensifier of affirmation. In some instances, people have sworn to tell the truth by placing their hands on a bible, and taking an oath, which ends with "so help me God." This has devolved into "so help me," meaning "I'm really telling the truth." One could render the patois pronunciation as "swelp me." I've never seen that before.

"I'm really telling the truth."

oh, that's it, thank you very much!)
now I know how to translate it!

I haven't exactly seen it, but I've durn sure heard it.

Oh yeah, i've heard it many times--i've just never seen it in print. There's a lot of that going on . . . hearing something which you wouldn't see in print. One of our little doggies has disgusting eating habits, so when she's out in the yard, i will remind her that i've got my eye on her by asking her "What are you eating?" But it comes out "Whachaeatin'?"

I saw it in an article titled Historical Slang and, as Setanta says, it means (God) so help me.

I also saw it in a Canadian headline, one political party swelped another, meaning swept away the power of another.

Perfectly natural example of spoken English. Setanta has raised a good point here that EFLs should heed. Everyday speech, including a lot of speech where one would expect a more formal SFE, sees this smooshing of words together.

The rules for this are exceedingly complex [so much so that much of it has yet to be describe] and these "rules" aren't something that should be actively and pointedly taught. Rather, a native speaking teacher or a highly competent EFL can model this type of fast speech until students pick up the rules naturally.

There is the tag, 'slang', on this thread.

"swelp me", gonna, hafta, wudave, etc. are not examples of slang. Reducing the sounds in speech is something that everyone, with the exception of robots, does.