Is it considered mockery if I get preoccupied with playing, or express certain facial gestures, or if my style of speaking about religious matters is not serious, or if I hear كلاماً لا يناسب أمور الدين (words that are inappropriate for religious matters)?

The whisperings (waswas) have reached a great extent with you, and what you mentioned in your question is not mockery of religion. We advise you to turn away from these whisperings and completely ignore them, for this is the way to cure them. Occupy your time and energy with learning Fiqh (Islamic jurisprudence), Hadith (prophetic traditions), and Tafsir (Qur'anic exegesis), and by reading the Sira (biography of the Prophet) and the history of the righteous predecessors. Engage yourself in teaching your siblings and children.