Its odd that one would drop down twice.
Could this be the case of an unselected deity for your class?
Did you pick a class that requires a compulsory feat? (Picking up ranger, but not using the lvl 1 bonus feat to select your Favoured Enemy)?
Without knowing your classes or class selection, its difficult to debug. Though in the case of a delevel the reason should be listed in yellow in your combat log.
You can also reupdate your XP/due level up quickly by dropping a gold piece and picking it up again, or relogging, to retake your level, and maybe resting again after successfully getting level 3 will give you back level 4.