After oil and filter change an increase in leakage (enough to lose it down to minimum) probably has something to do with said oil/filter change. Check valve cover gasket, filter gasket, oil pan plug and gasket (even if suction system was used to change oil).
Who changed the oil/filter? Have them check their work first. All these things are relatively cheap/easy to check before assuming the dreaded head gasket scenario. Head gasket should be presumed innocent until proven guilty. "If the head gasket fits, you must aquit".. " If it seals, there's no appeal"...sorry, don't know what came over me...it'll never happen again.
The Golden Rule
1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)