What ALAKTORN says is true. As someone who is on the staff at DCTP, I know, probably more than most, the lengths that the staff goes through to keep bringing you the manga. We have real life to deal with, jobs and school. On top of that, translating Japanese isn't exactly easy. Then you have the cleaning and the editing and raw acquisition. Everything takes time, and we only want to provide the best possible scanlations.
Also, since many fans don't realize this, Shonen Sunday is a big misnomer, since the magazine isn't actually released on Sunday. It is released on Wednesday.
Finally... Sometimes there are breaks. Always check the end of the chapter to see which copy of Shonen Sunday it is coming out in. You can check the issue and date of release at websunday.