Is it obligatory to perform the Hajj again after becoming committed to religious practice and wearing the hijab and niqab, knowing that the Hajj was previously performed years before this commitment and before wearing the hijab?

Your past Hajj is sufficient for the Hajj of Islam, even if you were negligent in your commitment and hijab (definition), unless you were abandoning prayer and continued to abandon it during Hajj. In that case, your Hajj is not valid, because abandoning prayer is disbelief (kufr), and Hajj is not valid alongside disbelief. Indeed, one who does not pray is a disbeliever whose Hajj and acts of worship are not accepted.