I am tempted to pour out my marriage problems as a second wife on social media. Is that wise?

Pouring out marriage problems on social media usually brings regret, not a solution. What is posted is hard to take back, easily misread, and can shame you, your husband and your children. It also exposes faults that Islam tells us to cover. Instead of posting, choose one trustworthy and knowledgeable person to confide in, or take it straight to Allah in prayer. If you need real help, see a counsellor who keeps confidentiality. Save your energy for solving the problem, not broadcasting it for passing sympathy. The gap between an angry feeling and typing fingers usually needs only one night to think again. See mental health.