Mental prayer is simply interior conversation with God. We “invite” Him to participate in all our thoughts and actions by turning the monologue in our mind (talking to ourselves) into a dialogue with Him. Mental prayer is something that can be done in all times and circumstances. So to answer your question, yes it does sound as if you’re already engaged in on-going mental prayer.
Since I see you are new to Carmel I highly recommend “The Practice of the Presence of God” by Brother Lawrence, a Carmelite lay brother. He describes all this so wonderfully and one of the key points he makes is that he saw no difference between the “formal” time required for mental prayer with what he did at all other times of the day.
Think of mental prayer as an “interior, loving conversation between friends” . . . prayer of the heart in a manner of speaking. As such it should rise beyond the simple recitation of vocal prayer. These prayers, while good in their own right, should lead us to mental prayer once our hearts are so moved.
Sometimes our mental prayer may be spontaneous conversation . . . and other times it might simply be a brief, repeated aspiration such as “Thy will be done.” And, as one is drawn toward interior recollection, it even becomes wordless . . . a simple glance toward Him or “interior smile” in the words of Brother Lawrence.
Hope this helps,