As long as you can get at-least 24 consecutive hours rest in the weeks you drive HGVs in-scope of EU regulations you should be able to legally work a driving shift every second week.
Some people manage to get 45 hours rest and still do a HGV driving shift every week but obviously that will depend on the hours you work.
In weeks that you drive in-scope of EU regulations the work you do in your usual job counts as other work and legally should be recorded as such on charts or printouts.