It may not have anything to do with aerodynamics, but your gear ratio.
The website for the Merida Cyclocross 3 does not list the specifications, but the Merida 4 does indicate that, like most cyclocross bikes, it comes with a compact crankset, with the largest chainring at 46 teeth.
You should be able to stick with the group, but you will need to be spinning faster than you might be comfortable with. The compact cranks make going up hills a bit easier, but at higher speeds you will spin a faster rpm than typical cranks for the same speed, meaning you'll be working harder then the group and may tire out sooner, especially on flat to rolling terrain.
For the higher speeds, make sure you have an 11 tooth cog in the rear cassette and that will help (again, specs for the Merida 4 indicate 12-28).
You can find some more in-depth info googling: "compact cranks vs standard"
also: Why might a compact drivetrain be frowned upon?