The term "omgwthigo" is an acronym that stands for "Oh my gosh what the heck is going on?!" normally used when the person either truly is clueless on what is happening (usually wherever the other person is communicationg from) or as an expression while in a confusing online conversation, mostly with more than two people involved.
The longer version is more explicit, and self explanatory on what it is
User 1 says: There is no way that this is happening
User 2 says: I know srsly this is mssd up
Used 3 says: Unbelievable
User 1 says: Yeah
User 4 says: omgwthigo