Sorry, but this is incorrect. A person isn’t afforded a “free sin pass” just by saying “I wonder if this is a mortal sin.” The three conditions are:
- Grave matter
- Full knowledge (not "and that it is a grave matter)
- Deliberate consent
See the CCC article 8 starting at paragraph 1846 for a discussion of sin and of what constitutes a mortal sin. You’ll note full knowledge is qualified by paragraph 1859 which states,
Mortal sin requires full knowledge and complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God’s law. It also implies a consent sufficiently deliberate to be a personal choice.
Feigned ignorance and hardness of heart do not diminish, but rather increase,
the voluntary character of a sin.
and paragraph 1860,
But
no one is deemed to be ignorant of the principles of the moral law, which are written in the conscience of every man. The promptings of feelings and passions can also diminish the voluntary and free character of the offense, as can external pressures or pathological disorders. Sin committed through malice, by deliberate choice of evil, is the gravest.